0000746458
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000088012Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000189766Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017686Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017688Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:CreditRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:BelowInvestmentGradeSecuritiesRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:InterestRateRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:LiquidityRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:MunicipalSecuritiesRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:TaxRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:MarketRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
oef:RiskLoseMoneyMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
oef:RiskNotInsuredDepositoryInstitutionMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsAndSalesMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsAndSalesMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsAndSalesMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017685Member
oef:AfterTaxesOnDistributionsAndSalesMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088012Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088012Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088012Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088012Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189766Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189766Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189766Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189766Member
2017-04-10
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017686Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017686Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017686Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017686Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017688Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017688Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017688Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017688Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesIndexMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesIndexMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesIndexMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesIndexMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPMunicipalBond50InvestmentGrade50HighYieldIndexreflectsnodeductionforfeesexpensesortaxesMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPMunicipalBond50InvestmentGrade50HighYieldIndexreflectsnodeductionforfeesexpensesortaxesMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPMunicipalBond50InvestmentGrade50HighYieldIndexreflectsnodeductionforfeesexpensesortaxesMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPMunicipalBond50InvestmentGrade50HighYieldIndexreflectsnodeductionforfeesexpensesortaxesMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2016-01-01
2016-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2017-01-01
2017-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2018-01-01
2018-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2019-01-01
2019-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2020-01-01
2020-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2021-01-01
2021-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2022-01-01
2022-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2023-01-01
2023-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2024-01-01
2024-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006471Member
ck0000746458:C000017685Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017691Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000189767Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000088013Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000088014Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:CreditRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:BelowInvestmentGradeSecuritiesRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:InterestRateRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:MunicipalSecuritiesRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:LossOfTaxExemptionsRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:LiquidityRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:MarketRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
oef:RiskLoseMoneyMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
oef:RiskNotInsuredDepositoryInstitutionMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsAndSalesMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsAndSalesMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsAndSalesMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017689Member
oef:AfterTaxesOnDistributionsAndSalesMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017691Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017691Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017691Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017691Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189767Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189767Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189767Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000189767Member
2017-04-10
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088013Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088013Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088013Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088013Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088014Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088014Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088014Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000088014Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPIntermediateTermNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPIntermediateTermNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesMember
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPIntermediateTermNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesMember
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:SPIntermediateTermNationalAMTFreeMunicipalBondIndexreflectsnodeductionforfeesexpensesortaxesMember
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2016-01-01
2016-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2017-01-01
2017-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2018-01-01
2018-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2019-01-01
2019-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2020-01-01
2020-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2021-01-01
2021-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2022-01-01
2022-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2023-01-01
2023-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2024-01-01
2024-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006472Member
ck0000746458:C000017689Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:LowYieldRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:MunicipalSecuritiesRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:InterestRateRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:CreditRisk1Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:LiquidityRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:LossOfTaxExemptionsRiskMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
oef:RiskLoseMoneyMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
oef:RiskNotInsuredDepositoryInstitutionMember
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017692Member
2026-10-01
2026-10-01
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017692Member
2025-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017692Member
2021-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:C000017692Member
2016-01-01
2025-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2016-01-01
2016-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2017-01-01
2017-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2018-01-01
2018-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2019-01-01
2019-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2020-01-01
2020-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2021-01-01
2021-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2022-01-01
2022-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2023-01-01
2023-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2024-01-01
2024-12-31
0000746458
ck0000746458:AMERICANCENTURYMUNICIPALTRUSTMember
ck0000746458:S000006473Member
ck0000746458:C000017692Member
2025-01-01
2025-12-31
iso4217:USD
pure
485BPOS
0000746458
false
0.0046
0.0924
0.0146
0.0939
0.0465
0.0586
-0.1310
0.0589
0.0539
0.0295
-0.0037
0.0477
0.0092
0.0670
0.0476
0.0200
-0.0789
0.0543
0.0165
0.0452
0.0014
0.0045
0.0101
0.0105
0.0036
0.0001
0.0084
0.0301
0.0306
0.0236
2026-09-28
N-1A
AMERICAN CENTURY MUNICIPAL TRUST
2026-10-01
High-Yield Municipal Fund
Investment Objective
The fund seeks high current income that is exempt from federal income tax.
The fund also seeks capital appreciation as a secondary objective.
Fees and Expenses
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may also pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Calculation of Sales Charges</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> on page 12 of the fund’s prospectus, </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Appendix A</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> of the fund’s prospectus and </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Sales Charges</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> in </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Appendix B</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> of the statement of additional information.</span>
You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds.
100000
Shareholder Fees (fees paid directly from your investment)
0
0
0
0.0450
0
0
0
0
0
0.0100
25
0
0
0
0
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
0.0059
0.0039
0.0036
0.0059
0.0059
0
0
0
0.0025
0.0100
0.0001
0.0001
0.0001
0.0001
0.0001
0.0060
0.0040
0.0037
0.0085
0.0160
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:9pt;font-style:italic;font-weight:400;line-height:120%">Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of the purchase.</span>
Example
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
61
193
335
751
41
129
225
506
38
119
208
469
533
709
901
1452
163
506
872
1698
Portfolio Turnover
<div style="margin-bottom:6pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 49% of the average value of its portfolio.</span></div>
0.49
Principal Investment Strategies
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund invests in municipal and other debt securities with an emphasis on high-yield securities. A high-yield security is one that has been rated below investment-grade, or determined by the investment advisor to be of similar quality.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Under normal market conditions, the portfolio managers invest at least 80% of the fund’s net assets in municipal securities with interest payments exempt from federal income tax. Some of these investments in municipal securities are not necessarily exempt from the federal alternative minimum tax.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The portfolio managers seek to invest in securities that will result in a high yield for the fund. To accomplish this, the portfolio managers buy securities that are rated below investment-grade, including so-called junk bonds and bonds that are in technical or monetary default. Issuers of these securities often have short financial histories or have questionable credit or have had and may continue to have problems making interest and principal payments.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The portfolio managers also may buy unrated securities if they determine such securities meet the investment objectives of the fund.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The managers typically buy long-term and intermediate-term municipal securities, but may purchase municipal securities of any duration. The managers attempt to keep the weighted average maturity of the fund at 10 years or longer.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Although the fund invests principally for income, it also employs techniques designed to realize capital appreciation. For example, the portfolio managers may select bonds with maturities and coupon rates that position the fund for potential capital appreciation for a variety of reasons, including their view on the direction of future interest-rate movements and the potential for a credit upgrade.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">When determining whether to sell a security, portfolio managers consider, among other things, current and anticipated changes in interest rates, the credit quality of a particular issuer, comparable alternatives, general market conditions and any other factor deemed relevant by the portfolio managers.</span></div>
Under normal market conditions, the portfolio managers invest at least 80% of the fund’s net assets in municipal securities with interest payments exempt from federal income tax.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Credit Risk</span> – Debt securities, even investment-grade debt securities, are subject to credit risk. Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease. As a result, the fund’s share price could also decrease. Changes in the credit rating of a debt security held by the fund could have a similar effect. The fund’s investments often have high credit risk, which helps the fund pursue a higher yield than more conservatively managed bond funds.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Below Investment-Grade Securities Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Issuers of lower rated, high-yield securities are more vulnerable to real or perceived economic changes (such as an economic downturn or a prolonged period of rising interest rates), political changes, or adverse developments specific to the issuer. Adverse economic, political and other developments may be more likely to cause an issuer of low-quality bonds to default on its obligation to pay interest and principal due under its securities. The fund invests a significant part of its assets in securities rated below investment-grade or that are unrated, including bonds that are in technical or monetary default. By definition, the issuers of many of these securities have had and may continue to have problems making interest and principal payments. High-yield securities are speculative.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Interest Rate Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – When interest rates change, the fund’s share value will be affected. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. Because the fund typically invests in intermediate-term and long-term bonds, the fund’s interest rate risk is generally higher than for funds with shorter-weighted average maturities, such as money market and short-term bond funds. A period of rising interest rates may negatively affect the fund’s performance.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Liquidity Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – The fund may also be subject to liquidity risk. During periods of market turbulence or unusually low trading activity, to meet redemptions, it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions, including increases in interest rates and credit spreads may adversely affect the liquidity of the fund’s investments.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Municipal Securities Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Because the fund invests principally in municipal securities, it will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. The fund may have a higher level of risk than funds that invest in a larger universe of securities.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Tax Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Some or all of the fund’s income may be subject to the federal alternative minimum tax. There is no guarantee that all of the fund’s income will remain exempt from federal or state income taxes. Income from municipal bonds held by a fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Market Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – The risk that the value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, war, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Principal Loss Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.</span>
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.</span></div>
Fund Performance
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the S&P Municipal Bond 50% Investment Grade/50% High Yield Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com. </span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.</span></div>
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
The table also shows returns for the S&P Municipal Bond 50% Investment Grade/50% High Yield Index, which the advisor considers to be more representative of the fund’s investment strategy.
The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
americancentury.com
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Calendar Year Total Returns
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">Highest Performance Quarter (4Q 2023): 7.86% Lowest Performance Quarter (1Q 2022): -6.50% </span></div><div style="margin-bottom:3pt;margin-top:3pt"><span><br/></span></div><div style="margin-bottom:3pt;margin-top:3pt;padding-left:4.5pt;text-indent:-4.5pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">As of June 30, 2026, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 3.32%.</span></div>
Highest Performance Quarter
2023-12-31
0.0786
Lowest Performance Quarter
2022-03-31
-0.0650
2026-06-30
Investor Class year-to-date return
0.0332
Average Annual Total ReturnsFor the calendar year ended December 31, 2025
Investor Class Return Before Taxes
0.0295
0.0111
0.0302
1998-03-31
Return After Taxes on Distributions
0.0295
0.0107
0.0299
1998-03-31
Return After Taxes on Distributions and Sale of Fund Shares
0.0353
0.0171
0.0319
1998-03-31
I Class Return Before Taxes
0.0315
0.0131
0.0323
2010-03-01
Y Class Return Before Taxes
0.0307
0.0134
0.0329
2017-04-10
A Class Return Before Taxes
-0.0204
-0.0007
0.0228
2003-01-31
C Class1 Return Before Taxes
0.0181
0.0010
0.0215
2002-07-24
S&P National AMT-Free Municipal Bond Index(reflects no deduction for fees, expenses or taxes)
(reflects no deduction for fees, expenses or taxes)
0.0377
0.0084
0.0228
S&P Municipal Bond 50% Investment Grade/50% High Yield Index(reflects no deduction for fees, expenses or taxes)
0.0366
0.0155
0.0329
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.</span></div>
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Intermediate-Term Tax-Free Bond Fund
Investment Objective
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund seeks safety of principal and high current income that is exempt from federal income tax.</span></div>
Fees and Expenses
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may also pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Calculation of Sales Charges</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> on page 12 of the fund’s prospectus, </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Appendix A</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> of the fund’s prospectus and </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Sales Charges</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> in </span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Appendix B</span> of the statement of additional information.
You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds.
100000
Shareholder Fees (fees paid directly from your investment)
0
0
0
0.0450
0
0
0
0
0
0.0100
25
0
0
0
0
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
0.0046
0.0026
0.0023
0.0046
0.0046
0
0
0
0.0025
0.0100
0.0001
0.0001
0.0001
0.0001
0.0001
0.0047
0.0027
0.0024
0.0072
0.0147
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:9pt;font-style:italic;font-weight:400;line-height:120%">Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of the purchase.</span>
Example
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
48
151
264
592
28
87
152
344
25
77
135
306
520
670
833
1305
150
466
803
1553
Portfolio Turnover
<div style="margin-bottom:6pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 38% of the average value of its portfolio.</span></div>
0.38
Principal Investment Strategies
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The portfolio managers principally buy investment-grade debt securities and, under normal market conditions, will invest at least 80% of the fund’s net assets in debt securities with interest payments exempt from federal income tax. The fund’s weighted average maturity will be not less than three years nor more than ten years. However, there is no maturity limit on individual securities.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The portfolio managers also may buy investment-grade debt securities with interest payments exempt from regular federal income tax, but not exempt from the federal alternative minimum tax. No more than 20% of the fund’s assets may be invested in these securities.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Although the fund invests principally in investment-grade securities, up to 20% of the value of the fund’s net assets may be invested in below investment-grade securities, also known as junk bonds. The fund also may invest in securities which, while not rated, are determined by the portfolio managers to be of comparable credit quality to those rated below investment-grade.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">When determining whether to sell a security, portfolio managers consider, among other things, current and anticipated changes in interest rates, the credit quality of a particular issuer, comparable alternatives, general market conditions and any other factor deemed relevant by the portfolio managers.</span></div>
The portfolio managers principally buy investment-grade debt securities and, under normal market conditions, will invest at least 80% of the fund’s net assets in debt securities with interest payments exempt from federal income tax.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Credit Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Debt securities, even investment-grade debt securities, are subject to credit risk. Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease. As a result, the fund’s share price could also decrease. Changes in the credit rating of a debt security held by the fund could have a similar effect.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Below Investment-Grade Securities Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Issuers of lower rated, high yield securities are more vulnerable to real or perceived economic changes (such as an economic downturn or a prolonged period of rising interest rates), political changes or adverse developments specific to an issuer. These factors may be more likely to cause an issuer of low quality bonds to default on its obligations. High-yield securities are speculative.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Interest Rate Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Investments in debt securities are also sensitive to interest rate changes. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. The fund’s interest rate risk is moderate under normal market conditions, but it may fluctuate as the portfolio managers reposition the fund in response to changing market conditions. A period of rising interest rates may negatively affect the fund’s performance.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Municipal Securities Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – The fund invests principally in municipal securities and will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. By investing primarily in municipal securities, the fund may have a higher level of risk than funds that invest in a larger universe of securities.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Loss of Tax-Exemptions Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – There is no guarantee that all of the fund’s income will be exempt from federal or state income taxes. Income from municipal bonds held by the fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Liquidity Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – The fund may also be subject to liquidity risk. During periods of market turbulence or unusually low trading activity, in order to meet redemptions it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions, including increases in interest rates and credit spreads may adversely affect the liquidity of the fund’s investments.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Market Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – The value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, war, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Principal Loss Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.</span>
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.</span></div>
Fund Performance
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The table also shows returns for the S&P Intermediate Term National AMT-Free Municipal Bond Index, which the advisor considers to be more representative of the fund’s investment strategy. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.</span></div>
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
The table also shows returns for the S&P Intermediate Term National AMT-Free Municipal Bond Index, which the advisor considers to be more representative of the fund’s investment strategy.
The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
americancentury.com
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Calendar Year Total Returns
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">Highest Performance Quarter (4Q 2023): 6.58% Lowest Performance Quarter (1Q 2022): -5.40% </span></div><div style="margin-bottom:3pt;margin-top:3pt"><span><br/></span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">As of June 30, 2026, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 1.86%.</span></div>
Highest Performance Quarter
2023-12-31
0.0658
Lowest Performance Quarter
2022-03-31
-0.0540
2026-06-30
Investor Class year-to-date return
0.0186
Average Annual Total ReturnsFor the year ended December 31, 2025
Investor Class Return Before Taxes
0.0452
0.0103
0.0217
1987-03-02
Return After Taxes on Distributions
0.0452
0.0103
0.0217
1987-03-02
Return After Taxes on Distributions and Sale of Fund Shares
0.0408
0.0143
0.0229
1987-03-02
I Class Return Before Taxes
0.0473
0.0123
0.0237
2003-04-15
Y Class Return Before Taxes
0.0486
0.0128
0.0256
2017-04-10
A Class Return Before Taxes
-0.0043
-0.0015
0.0145
2010-03-01
C Class1 Return Before Taxes
0.0358
0.0004
0.0130
2010-03-01
S&P National AMT-Free Municipal Bond Index(reflects no deduction for fees, expenses or taxes)
(reflects no deduction for fees, expenses or taxes)
0.0377
0.0084
0.0228
S&P Intermediate Term National AMT-Free Municipal Bond Index(reflects no deduction for fees, expenses or taxes)
0.0465
0.0122
0.0225
<div style="margin-bottom:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.</span></div>
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Tax-Free Money Market Fund
Investment Objective
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund seeks safety of principal and high current income that is exempt from federal income tax.</span></div>
Fees and Expenses
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund.</span>
Shareholder Fees (fees paid directly from your investment)
25
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of your investment)
0.0049
0
0
0.0049
Example
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
50
157
275
617
Principal Investment Strategies
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The fund is a retail money market fund that invests in municipal money market securities. The securities purchased by the fund are subject to the maturity, quality, diversification, and other requirements of Rule 2a-7 under the Investment Company Act of 1940, as amended. Although the fund seeks to maintain a $1.00 share price, there is no guarantee it will be able to do so.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Under normal market conditions, the fund invests at least 80% of its net assets in cash-equivalent, high-quality debt securities with interest payments exempt from federal income tax. Cities, counties, other municipalities and U.S. territories may issue these securities. A high-quality debt security is one that an independent rating agency rates in its top two credit quality categories or that the advisor determines to be of comparable credit quality.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The portfolio managers also may buy cash-equivalent, high-quality debt securities with interest payments exempt from regular federal income tax, but not exempt from the federal alternative minimum tax. Cities, counties, and other municipalities usually issue these securities (called private activity bonds) to fund for-profit private projects, such as hospitals and athletic stadiums. The fund may invest no more than 20% of its assets in these securities.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">When determining whether to buy or sell a security, portfolio managers may consider current and anticipated changes in interest rates, issuer credit quality, comparable alternatives, diversification limits, and general market conditions.</span></div>
Under normal market conditions, the fund invests at least 80% of its net assets in cash-equivalent, high-quality debt securities with interest payments exempt from federal income tax.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Low Yield Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Because high-quality debt securities are among the safest securities available, the interest they pay is among the lowest for income-paying securities. Accordingly, the yield on this fund will likely be lower than the yield on funds that invest in lower-quality or longer-term securities.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Municipal Securities Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Because the fund invests principally in municipal securities, it will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. By investing primarily in municipal securities, the fund may have a higher level of risk than funds that invest in a larger universe of securities.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Interest Rate Risk</span> – Interest rate risk means that the value of debt securities and the funds that hold them decline as interest rates rise. A period of rising interest rates may negatively affect the fund’s performance.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Credit Risk</span> – Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease.
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Liquidity Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – Liquidity risk means that during periods of market turbulence or unusually low trading activity, to meet redemptions it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions may adversely affect the liquidity of the fund’s investments. If liquidity decreases too much, the fund may impose a fee on the sale of shares or temporarily suspend redemptions.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Loss of Tax-Exemptions Risk</span><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%"> – There is no guarantee that all of the fund’s income will be exempt from federal or state income taxes. Income from municipal bonds held by the fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.</span>
<span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%;padding-left:5.5pt">Principal Loss Risk</span> – You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.
An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Fund Performance
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, visit americancentury.com.</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:400;line-height:120%">Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.</span></div>
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares.
The fund’s past performance is not necessarily an indication of how the fund will perform in the future.
americancentury.com
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Calendar Year Total Returns
<div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">Highest Performance Quarter (4Q 2023): 0.83% Lowest Performance Quarter (1Q 2021): 0.00%</span></div><div style="margin-bottom:3pt;margin-top:3pt"><span><br/></span></div><div style="margin-bottom:3pt;margin-top:3pt"><span style="color:#000000;font-family:'Times New Roman',serif;font-size:10pt;font-weight:700;line-height:120%">As of June 30, 2026, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 0.97%.</span></div>
Highest Performance Quarter
2023-12-31
0.0083
Lowest Performance Quarter
2021-03-31
0.0000
2026-06-30
Investor Class year-to-date return
0.0097
Average Annual Total Returns For the calendar year ended December 31, 2025
Investor Class
0.0236
0.0185
0.0122
Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of the purchase.
C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.
Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of the purchase.
C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.