The following table analyzes other intangible assets movements in the year:


(in millions)	2025
Gross cost at January 1	$	331.8
Additions		10.8
Exchange effect		16.7
Gross cost at June 30		359.3
Accumulated amortization at January 1		(266.4	)
Amortization expense		(5.9	)
Exchange effect		(8.7	)
Accumulated amortization at June 30		(281.0	)
Net book amount at June 30	$	78.3

The amortization expense for the six months ended June 30, 2025 was $5.9 million (six months ended June 30, 2024 – $6.0 million).

In 2025, we have capitalized $10.8 million in relation to our internally developed software for a new Enterprise Resource Planning (“ERP”) system covering all our regions. The project is ongoing and is currently expected to complete in 2026. The expenses capitalized include the acquisition costs for the software as well as the external consultancy costs and the internal employee costs relating to the software development.