On July 24, 2025, Pinnacle Financial Partners, Inc., a Tennessee corporation (“Pinnacle”), Synovus Financial Corp., a Georgia corporation (“Synovus”), and Steel Newco Inc., a newly formed Georgia corporation jointly owned by Pinnacle and Synovus (“Newco”), entered into an Agreement and Plan of Merger (as amended from time to time, the “merger agreement”), pursuant to which, on the terms and subject to the conditions thereof, Pinnacle and Synovus have agreed to a business combination transaction in which each of Pinnacle and Synovus will simultaneously merge with and into Newco (such mergers, collectively, the “merger”), with Newco as the surviving entity and named Pinnacle Financial Partners, Inc. Immediately following the completion of the merger, Pinnacle Bank, a Tennessee-chartered bank and wholly owned subsidiary of Pinnacle (“Pinnacle Bank”), will become a member bank of the Federal Reserve System (the “FRS membership”), and immediately following the effectiveness of the FRS membership, Synovus Bank, a Georgia-chartered bank and wholly owned subsidiary of Synovus (“Synovus Bank”), will merge with and into Pinnacle Bank, with Pinnacle Bank as the surviving bank (the “bank merger”).

In the merger, (i) holders of Pinnacle common stock will receive one (1) share of Newco common stock for each share of Pinnacle common stock they own (the “Pinnacle exchange ratio” and such shares, the “Pinnacle merger consideration”), and (ii) holders of Synovus common stock will receive 0.5237 shares of Newco common stock for each share of Synovus common stock they own (the “Synovus exchange ratio” and such shares, the “Synovus merger consideration”), in each case, excluding certain shares owned by Synovus or Pinnacle that will be cancelled and retired in connection with the merger. Holders of Synovus common stock will receive cash in lieu of any fractional shares of Newco common stock they would otherwise be entitled to receive. Based on the closing price of Synovus common stock on the New York Stock Exchange (“NYSE”) on July 21, 2025, the last trading day prior to media reports regarding a potential transaction involving Synovus, the Synovus exchange ratio represented a Synovus per share of $61.18, a transaction value of $8.6 billion and an approximate 10% premium to Synovus’ per share value on an unaffected basis. The value of Newco common stock at the time of the completion of the merger could be greater than, less than or the same as the value of Newco common stock contemplated by the Pinnacle exchange ratio and the Synovus exchange ratio on the date of the accompanying joint proxy/prospectus. We urge you to obtain current market quotations of Pinnacle common stock (trading symbol “PNFP”) and Synovus common stock (trading symbol “SNV”). After the completion of the merger, Newco common stock will be listed on the NYSE under trading symbol “PNFP.”

In addition, each share of Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series D (“Synovus series D preferred stock”) and Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series E (“Synovus series E preferred stock”, and together with Synovus series D preferred stock, “Synovus preferred stock”) outstanding immediately prior to the effective time will be converted into the right to receive one (1) share of an applicable newly created series of Newco preferred stock with terms that are not materially less favorable than the terms of the applicable series of outstanding Synovus preferred stock. Likewise, following the completion of the merger, each outstanding Pinnacle depositary share representing a 1/40th interest in a share of Pinnacle 6.75% Fixed-Rate Non-Cumulative Perpetual Preferred Stock, series B (the “Pinnacle series B preferred stock”) will become a Newco depositary share representing a 1/40th interest in a share of an applicable newly created series of Newco preferred stock with terms that are not materially less favorable than the terms of such Pinnacle series B preferred stock. The shares of Synovus series D preferred stock and Synovus series E preferred stock are currently listed on the NYSE under the symbols “SNV-PrD” and “SNV-PrE,” respectively, and the Pinnacle depositary shares representing a 1/40th interest in a share of Pinnacle series B preferred stock are listed on the NASDAQ under the symbol “PNFPP.” After the completion of the merger, Newco series A preferred stock will be listed on the NYSE under trading symbol “PNFP-PrA,” Newco series B preferred stock will be listed on the NYSE under trading symbol “PNFP-PrB,” and depositary shares in respect of Newco series C preferred stock will be listed on the NYSE under the trading symbol “PNFP-PrC.”

The simultaneous mergers of Pinnacle and Synovus with and into Newco are each intended to qualify as a reorganization for U.S. federal income tax purposes. Accordingly, holders of Pinnacle common stock or Synovus common stock generally will not recognize any gain or loss for federal income tax purposes on the exchange of shares of Pinnacle common stock or Synovus common stock for Newco common stock in the merger, except with respect to any cash in lieu of a fractional share of Newco common stock received by holders of Synovus common stock.

Based on the number of shares of Pinnacle common stock and Synovus common stock outstanding or reserved for issuance, Newco expects to issue approximately 150,255,729 shares of Newco common stock to holders of Pinnacle common stock and Synovus common stock in the aggregate in the merger. Following the completion of the merger, we expect that former Pinnacle shareholders will own approximately 51.5% and former Synovus shareholders will own approximately 48.5% percent of the Newco common stock.

Pinnacle and Synovus will each hold a virtual special meeting of our respective shareholders in connection with the merger. At our respective special meetings, in addition to other business, Pinnacle will ask holders of its common stock and Synovus will ask holders of its common stock to approve the merger.

Information about these meetings and the merger is contained in this document. In particular, see “Risk Factors” beginning on page 49. We urge you to read this document carefully and in its entirety.

Holders of Pinnacle series B preferred stock and holders of depositary shares representing interests in the shares of Pinnacle series B preferred stock are not entitled to and are not requested to vote at the Pinnacle special meeting. Holders of Synovus preferred stock are not entitled to and are not requested to vote at the Synovus special meeting.

The special meeting of holders of Pinnacle common stock will be held virtually via the Internet on November 6, 2025 at www.virtualshareholdermeeting.com/PNFP2025SM, at 9:00 a.m. Eastern Time. The special meeting of holders of Synovus common stock will be held virtually via the Internet on November 6, 2025 at www.virtualshareholdermeeting.com/SNV2025SM, at 9:00 a.m. Eastern Time.

Whether or not you plan to attend your special meeting, please vote as soon as possible to make sure that your shares are represented at the meeting. If you do not vote your shares of common stock, it will have the same effect as voting “AGAINST” the merger.

Each of our boards of directors unanimously recommends that holders of common stock vote “FOR” each of the proposals to be considered at the respective special meetings. We strongly support this combination of our companies and join our boards in their recommendations.

This joint proxy statement/prospectus provides you with detailed information about the merger agreement and the merger. It also contains or references information about Pinnacle and Synovus and certain related matters. You are encouraged to read this joint proxy statement/prospectus carefully. In particular, you should read the “Risk Factors” section beginning on page 49 for a discussion of the risks you should consider in evaluating the proposed merger and how it will affect you. You can also obtain information about Pinnacle and Synovus from documents that have been filed with the Securities and Exchange Commission that are incorporated into this joint proxy statement/prospectus by reference.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger or determined if this document is accurate or complete. Any representation to the contrary is a criminal offense.

The securities to be issued in the merger are not savings or deposit accounts or other obligations of any bank or non-bank subsidiary of either Pinnacle or Synovus, and they are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

The accompanying joint proxy statement/prospectus is dated [ ], 2025, and is first being mailed to holders of Pinnacle common stock and holders of Synovus common stock on or about [   ], 2025.

The accompanying joint proxy statement/prospectus incorporates important business and financial information about Pinnacle and Synovus from other documents that are not included in or delivered with this document. This information is available to you without charge upon your written or oral request. You can obtain the documents incorporated by reference in this document through the Securities and Exchange Commission website at http://www.sec.gov or by requesting them in writing, by e-mail or by telephone at the appropriate address below:

You will not be charged for any of these documents that you request. To obtain timely delivery of these documents, you must request them no later than five (5) business days before the date of the applicable special meeting. This means that holders of Pinnacle common stock requesting documents must do so by October 30, 2025, in order to receive them before the Pinnacle special meeting, and holders of Synovus common stock requesting documents must do so by October 30, 2025, in order to receive them before the Synovus special meeting.

No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this document. This document is dated [   ], 2025, and you should assume that the information in this document is accurate only as of such date. You should assume that the information incorporated by reference into this document is accurate as of the date of such incorporated document. Neither the mailing of this document to holders of Pinnacle common stock or holders of Synovus common stock, nor the issuance by Newco of shares of Newco common stock, Newco preferred stock or depositary shares in respect of Newco preferred stock in connection with the merger will create any implication to the contrary.

This document does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Except where the context otherwise indicates, information contained in, or incorporated by reference into, this document regarding Pinnacle has been provided by Pinnacle and information contained in, or incorporated by reference into, this document regarding Synovus has been provided by Synovus.

See “Where You Can Find More Information” beginning on page 192 of the accompanying joint proxy statement/prospectus for further information.

 

To Pinnacle Shareholders:

On July 24, 2025, Pinnacle Financial Partners, Inc. (“Pinnacle”), Synovus Financial Corp. (“Synovus”) and Steel Newco Inc. (“Newco”) entered into an Agreement and Plan of Merger (as amended from time to time, the “merger agreement”), a copy of which is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of Pinnacle common stock (the “Pinnacle special meeting”) will be held virtually via the Internet on November 6, 2025 at 9:00 a.m. Eastern Time at www.virtualshareholdermeeting.com/PNFP2025SM. We are pleased to notify you of and invite you to the Pinnacle special meeting.

At the Pinnacle special meeting you will be asked to vote on the following matters:

The Pinnacle special meeting is expected to be held in a virtual-only format conducted via live webcast. In order to attend the Pinnacle special meeting via remote communication, you must access the virtual meeting at www.virtualshareholdermeeting.com/PNFP2025SM. You also will need a control number, which is the 16-digit number on your proxy card. Once admitted to the Pinnacle special meeting, you will be able to vote your shares in accordance with the instructions provided on the meeting website.

The board of directors of Pinnacle has fixed the close of business on September 26, 2025 as the record date for the Pinnacle special meeting. Only holders of record of Pinnacle common stock and depositary shares in respect of Pinnacle series B preferred stock as of the close of business on the record date for the Pinnacle special meeting are entitled to notice of the Pinnacle special meeting or any adjournment or postponement thereof. Although holders of depositary shares in respect of Pinnacle series B preferred stock are entitled to notice of the Pinnacle special meeting, only holders of record of Pinnacle common stock as of the close of business on the record date for the Pinnacle special meeting are entitled to vote at the Pinnacle special meeting or any adjournment or postponement thereof.

Pinnacle has determined that holders of Pinnacle common stock and holders of Pinnacle depositary shares are not entitled to appraisal or dissenters’ rights with respect to the proposed merger under Title 48 of Chapter 23 of the Tennessee Business Corporation Act.

The Pinnacle board of directors unanimously recommends that holders of Pinnacle common stock vote “FOR” the Pinnacle merger proposal, “FOR” the Pinnacle compensation proposal and “FOR” the Pinnacle adjournment proposal.

Your vote is important. We cannot complete the transactions contemplated by the merger agreement unless holders of Pinnacle common stock approve the merger agreement. The affirmative vote of a majority of all the votes entitled to be cast on the merger agreement by holders of Pinnacle common stock is required to approve the Pinnacle merger proposal. Whether or not you plan to attend the Pinnacle special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the Internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker or other nominee.

[   ], 2025

 

To Synovus Shareholders:

On July 24, 2025, Pinnacle Financial Partners, Inc. (“Pinnacle”), Synovus Financial Corp. (“Synovus”) and Steel Newco Inc. (“Newco”) entered into an Agreement and Plan of Merger (as amended from time to time, the “merger agreement”), a copy of which is attached as Annex A to the accompanying joint proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting of holders of Synovus common stock (the “Synovus special meeting”) will be held virtually via the Internet on November 6, 2025 at 9:00 a.m. Eastern Time at www.virtualshareholdermeeting.com/SNV2025SM. We are pleased to notify you of and invite you to the Synovus special meeting.

At the Synovus special meeting you will be asked to vote on the following matters:

The Synovus special meeting is expected to be held in a virtual-only format conducted via live webcast. In order to attend the Synovus special meeting via remote communication, you must access the virtual meeting at www.virtualshareholdermeeting.com/SNV2025SM. You also will need a control number, which is the 16-digit number on your proxy card. Once admitted to the Synovus special meeting, you will be able to vote your shares in accordance with the instructions provided on the meeting website.

The board of directors of Synovus has fixed the close of business on September 26, 2025 as the record date for the Synovus special meeting. Only holders of record of Synovus common stock as of the close of business on the record date for the Synovus special meeting are entitled to notice of the Synovus special meeting or any adjournment or postponement thereof. Only holders of record of Synovus common stock are entitled to vote at the Synovus special meeting or any adjournment or postponement thereof.

Synovus has determined that holders of Synovus common stock and holders of Synovus preferred stock are not entitled to appraisal or dissenters’ rights with respect to the proposed merger under Article 13 of the Georgia Business Corporation Code (the “GBCC”).

The Synovus board of directors unanimously recommends that holders of Synovus common stock vote “FOR” the Synovus merger proposal, “FOR” the Synovus compensation proposal and “FOR” the Synovus adjournment proposal.

Your vote is important. We cannot complete the transactions contemplated by the merger agreement unless holders of Synovus common stock approve the merger agreement. The affirmative vote of a majority of all of the votes entitled to be cast on the merger agreement by holders of Synovus common stock is required to approve the Synovus merger proposal. Whether or not you plan to attend the Synovus special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid

envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the Internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker or other nominee.

[   ], 2025

The following are some questions that you may have about the merger and the Pinnacle special meeting or the Synovus special meeting, and brief answers to those questions. We urge you to read carefully the remainder of this joint proxy statement/prospectus because the information in this section does not provide all of the information that might be important to you with respect to the merger and the Pinnacle special meeting or the Synovus special meeting. Additional important information is also contained in the documents incorporated by reference into this joint proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 192.

In this joint proxy statement/prospectus, unless the context otherwise requires:

will merge with and into Pinnacle Bank (the “bank merger”), with Pinnacle Bank as the surviving bank (the “combined bank”). In this joint proxy statement/prospectus, we refer to the closing of the transactions as the “closing” and the date on which the closing occurs as the “closing date.”

In order to complete the merger, among other things,

Pinnacle is holding a virtual special meeting of holders of Pinnacle common stock (the “Pinnacle special meeting”) to obtain approval of the Pinnacle merger proposal. Holders of Pinnacle depositary shares are entitled to notice of the special meeting, but holders of Pinnacle depositary shares are not entitled to and are not requested to vote at the Pinnacle special meeting. Holders of Pinnacle common stock and holders of Pinnacle depositary shares are not entitled to appraisal or dissenters’ rights with respect to the proposed merger under Title 48 of Chapter 23 of the Tennessee Business Corporation Act (the “TBCA”).

Holders of Pinnacle common stock will also be asked to approve the proposal to adjourn the Pinnacle special meeting to solicit additional proxies (i) if there are not sufficient votes at the time of the Pinnacle special meeting to approve the Pinnacle merger proposal or (ii) if adjournment is necessary or appropriate to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to holders of Pinnacle common stock (the “Pinnacle adjournment proposal”). Holders of Pinnacle common stock will also be asked to approve, on an advisory (non-binding) basis, the merger-related compensation payments that will or may be paid to Pinnacle’s named executive officers in connection with the merger (the “Pinnacle compensation proposal”).

Synovus is holding a virtual special meeting of holders of Synovus common stock (the “Synovus special meeting”) to obtain approval of the Synovus merger proposal. Holders of Synovus preferred stock are not entitled to notice of the special meeting, and are not entitled to and not requested to vote at the Synovus special meeting. Holders of Synovus common stock and holders of Synovus preferred stock are not entitled to appraisal or dissenters’ rights with respect to the proposed merger under Article 13 of the Georgia Business Corporation Code (the “GBCC”).

Holders of Synovus common stock will also be asked to approve the proposal to adjourn the Synovus special meeting to solicit additional proxies (i) if there are not sufficient votes at the time of the Synovus special meeting to approve the Synovus merger proposal or (ii) if adjournment is necessary or appropriate to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to holders of Synovus common stock (the “Synovus adjournment proposal”). Holders of Synovus common stock will also be asked to approve, on an advisory (non-binding) basis, the merger-related compensation payments that will or may be paid to Synovus’ named executive officers in connection with the merger (the “Synovus compensation proposal”).

This document is also a prospectus that is being delivered to holders of Pinnacle common stock, Pinnacle depositary shares, Synovus common stock, and Synovus preferred stock because, in connection with the merger, Newco is issuing shares of Newco common stock to holders of Pinnacle common stock and holders of Synovus common stock and is also issuing shares of newly created Newco preferred stock and Newco depositary shares in respect of Newco preferred stock to holders of Synovus preferred stock and holders of Pinnacle depositary shares, as applicable.

Under the terms of the merger agreement, each outstanding share of Pinnacle series B preferred stock will be converted into a newly created series of Newco preferred stock with terms that are not materially less favorable than the terms of the Pinnacle series B preferred stock (such Newco preferred stock, the “Newco series C preferred stock”). Upon the completion of the merger, each outstanding Pinnacle depositary share will become a Newco depositary share and will represent a 1/40th interest in a share of Newco series C preferred stock. In addition, (i) each share of Synovus series D preferred stock will be converted into the right to receive one (1) share of an applicable newly created series of Newco preferred stock with terms that are not materially less favorable than the terms of Synovus series D preferred stock (such Newco preferred stock, the “Newco series A preferred stock”) and (ii) each share of Synovus series E preferred stock will be

converted into the right to receive one (1) share of an applicable newly created series of Newco preferred stock with terms that are not materially less favorable than the terms of Synovus series E preferred stock (such Newco preferred stock, the “Newco series B preferred stock”)

This joint proxy statement/prospectus contains important information about the merger and the other proposals being voted on at the Pinnacle and Synovus special meetings. You should read it carefully and in its entirety. The enclosed materials allow you to have your shares of common stock voted by proxy without attending your meeting. Your vote is important and we encourage you to submit your proxy as soon as possible.

After the completion of the merger, Newco common stock will be listed on the New York Stock Exchange (the “NYSE”) under trading symbol “PNFP,” Newco series A preferred stock will be listed on the NYSE under trading symbol “PNFP-PrA,” Newco series B preferred stock will be listed on the NYSE under trading symbol “PNFP-PrB,” and depositary shares in respect of Newco series C preferred stock will be listed on the NYSE under the trading symbol “PNFP-PrC.”

In addition, as a result of the foregoing, after completion of the merger, Pinnacle and Synovus will no longer be public companies, Pinnacle common stock and depositary shares in respect of Pinnacle series B preferred stock will be delisted from the Nasdaq Stock Market (the “NASDAQ”) and Synovus common stock and Synovus preferred stock will be delisted from the NYSE. Both Pinnacle and Synovus will be deregistered under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and will cease to be publicly traded.

See the information provided in the section entitled “The Merger Agreement—Structure of the Merger” beginning on page 130 and the merger agreement for more information about the merger.

Even if you plan to attend the Pinnacle special meeting, Pinnacle recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to or become unable to attend the Pinnacle special meeting.

Even if you plan to attend the Synovus special meeting, Synovus recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to or become unable to attend the Synovus special meeting.

In order to complete the merger, among other things, holders of Pinnacle common stock must approve the Pinnacle merger proposal. Neither the approval of the Pinnacle compensation proposal nor the approval of the Pinnacle adjournment proposal are conditions to the obligation of Pinnacle to complete the merger.

In order to complete the merger, among other things, holders of Synovus common stock must approve the Synovus merger proposal. Neither the approval of the Synovus compensation proposal nor the approval of the Synovus adjournment proposal are conditions to the obligation of Synovus to complete the merger.

In considering the recommendations of the Pinnacle board of directors, holders of Pinnacle common stock should be aware that Pinnacle directors and executive officers may have interests in the merger that are different from, or in addition to, the interests of holders of Pinnacle common stock generally. For a more complete description of these interests, see the information provided in the section entitled “The Merger—Interests of Certain Pinnacle Directors and Executive Officers in the Merger” beginning on page 110.

In considering the recommendations of the Synovus board of directors, holders of Synovus common stock should be aware that Synovus directors and executive officers may have interests in the merger that are different from, or in addition to, the interests of holders of Synovus common stock generally. For a more complete description of these interests, see the information provided in the section entitled “The Merger—Interests of Certain Synovus Directors and Executive Officers in the Merger” beginning on page 117.

Each holder of Pinnacle common stock is entitled to cast one (1) vote on each matter properly brought before the Pinnacle special meeting for each share of Pinnacle common stock that such holder owned of record as of the record date. As of September 26, 2025, there were 77,559,967 outstanding shares of Pinnacle common stock.

Attendance at the special meeting is not required to vote. See below and the section entitled “The Pinnacle Special Meeting—Proxies” beginning on page 58 for instructions on how to vote your shares without attending the Pinnacle special meeting.

Each holder of Synovus common stock is entitled to cast one (1) vote on each matter properly brought before the Synovus special meeting for each share of Synovus common stock that such holder owned of record as of the record date. As of September 26, 2025, there were 138,811,843 outstanding shares of Synovus common stock.

Attendance at the special meeting is not required to vote. See below and the section entitled “The Synovus Special Meeting—Proxies” beginning on page 58 for instructions on how to vote your shares without attending the Synovus special meeting.

holders of Pinnacle common stock. Shares of Pinnacle common stock not present, and shares present and not voted, whether by broker non-vote, abstention or otherwise, will have the same effect as votes cast “AGAINST” the proposal to approve the merger agreement.

Pinnacle Proposal 2: Pinnacle compensation proposal. Approval of the Pinnacle compensation proposal requires that the votes cast in favor of the proposal at the Pinnacle special meeting exceed the votes cast opposing the proposal at the Pinnacle special meeting. Accordingly, an abstention or a broker non-vote or other failure to vote will have no effect on the outcome of the Pinnacle compensation proposal.

Pinnacle Proposal 3: Pinnacle adjournment proposal. Approval of the Pinnacle adjournment proposal requires that the votes cast in favor of the proposal at the Pinnacle special meeting exceed the votes cast opposing the proposal at the Pinnacle special meeting. Accordingly, an abstention or a broker non-vote or other failure to vote will have no effect on the outcome of the Pinnacle adjournment proposal.

Synovus Proposal 2: Synovus compensation proposal. Approval of the Synovus compensation proposal requires the affirmative vote of a majority of the votes cast by the holders of Synovus common stock at the Synovus special meeting. Accordingly, an abstention or a broker non-vote or other failure to vote will have no effect on the outcome of the Synovus compensation proposal.

Synovus Proposal 3: Synovus adjournment proposal. Approval of the Synovus adjournment proposal requires the affirmative vote of the holders of a majority of the Synovus common stock present or represented at the Synovus special meeting, whether or not a quorum is present. Accordingly, shares present and not voted, whether by broker non-vote, abstention or otherwise, will the same effect as votes cast “AGAINST” the Synovus adjournment proposal.

Beneficial Owners. If you hold shares of Pinnacle common stock or Synovus common stock in a brokerage or other account in “street name,” you are a “beneficial owner” and your shares may be voted at the Pinnacle special meeting or the Synovus special meeting, as applicable, by you as described below. If you choose to vote your shares virtually at the respective special meeting via the applicable special meeting website, you will need the control number, as described below.

Pinnacle special meeting. If you are a record holder of Pinnacle common stock, you will be able to attend the Pinnacle special meeting online, ask questions and vote during the meeting by visiting www.virtualshareholdermeeting.com/PNFP2025SM and following the instructions. Please have your 16-digit control number, which can be found on your proxy card, notice or email previously received, to access the meeting. If you are a beneficial owner, you also will be able to attend the Pinnacle special meeting online, ask questions and vote during the meeting by visiting www.virtualshareholdermeeting.com/PNFP2025SM and following the instructions. Please have your 16-digit control number, which can be found on the voting instructions provided by your bank, broker, trustee or other nominee, to access the meeting. Please review this information prior to the Pinnacle special meeting to ensure you have access.

Pinnacle encourages its shareholders to visit the meeting website above in advance of the Pinnacle special meeting to familiarize themselves with the online access process. The virtual Pinnacle special meeting platform is fully supported across browsers and devices that are equipped with the most updated version of applicable software and plugins. Shareholders should verify their internet connection prior to the Pinnacle special meeting. Technical support information is provided on the sign-in page for all shareholders. Shareholders will have substantially the same opportunities to participate in the virtual Pinnacle special meeting as they would have at a physical, in-person meeting. Shareholders as of the record date will be able to attend, vote, examine the shareholder list, and submit questions during a portion of the meeting via the online platform.

Synovus special meeting. If you are a record holder of Synovus common stock, you will be able to attend the Synovus special meeting online, ask questions and vote during the meeting by visiting www.virtualshareholdermeeting.com/SNV2025SM and following the instructions. Please have your 16-digit control number, which can be found on your proxy card, notice or email previously received, to access the meeting. If you are a beneficial owner, you also will be able to attend the Synovus special meeting online,

ask questions and vote during the meeting by visiting www.virtualshareholdermeeting.com/SNV2025SM and following the instructions. Please have your 16-digit control number, which can be found on the voting instructions provided by your bank, broker, trustee or other nominee, to access the meeting. Please review this information prior to the Synovus special meeting to ensure you have access.

Synovus encourages its shareholders to visit the meeting website above in advance of the Synovus special meeting to familiarize themselves with the online access process. The virtual Synovus special meeting platform is fully supported across browsers and devices that are equipped with the most updated version of applicable software and plugins. Shareholders should verify their internet connection prior to the Synovus special meeting. Technical support information is provided on the sign-in page for all shareholders. Shareholders will have substantially the same opportunities to participate in the virtual Synovus special meeting as they would have at a physical, in-person meeting. Shareholders as of the record date will be able to attend, vote, examine the shareholder list, and submit questions during a portion of the meeting via the online platform.

Even if you plan to attend the Pinnacle special meeting or the Synovus special meeting virtually, as applicable, Pinnacle and Synovus recommend that you vote your shares in advance as described below so that your vote will be counted if you later decide not to or become unable to attend the respective special meeting.

Additional information on attending the virtual special meetings can be found under the section entitled “The Pinnacle Special Meeting” on page 56 and under the section entitled “The Synovus Special Meeting” on page 62.

If you are a record holder of Pinnacle common stock or Synovus common stock, you can vote your shares by proxy over the Internet, by telephone or by mail by following the instructions provided in the enclosed proxy card. If you hold shares beneficially in “street name” as a beneficial owner of Pinnacle common stock or Synovus common stock, you should follow the voting instructions provided by your bank, broker, trustee or other nominee.

Additional information on voting procedures can be found under the section entitled “The Pinnacle Special Meeting” on page 56 and under the section entitled “The Synovus Special Meeting” on page 62.

instructions from beneficial owners. However, banks, brokers and other nominees are not allowed to exercise their voting discretion with respect to the approval of matters determined to be “non-routine” without specific instructions from the beneficial owner.

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only count toward a quorum if at least one (1) proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. It is expected that all proposals to be voted on at each of the Pinnacle special meeting and the Synovus special meeting will be “non-routine” matters, and, as such, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the Pinnacle special meeting or the Synovus special meeting. If your bank, broker, trustee or other nominee holds your shares of Pinnacle common stock or Synovus common stock in “street name,” such entity will vote your shares of Pinnacle common stock or Synovus common stock only if you provide instructions on how to vote by complying with the instructions provided to you by your bank, broker, trustee or other nominee with this joint proxy statement/prospectus.

If you are a beneficial owner of Pinnacle common stock and you do not instruct your bank, broker, trustee or other nominee on how to vote your shares of Pinnacle common stock:

If you are a beneficial owner of Synovus common stock and you do not instruct your bank, broker, trustee or other nominee on how to vote your shares of Synovus common stock:

For purposes of the Synovus special meeting, an abstention occurs when a Synovus shareholder attends the Synovus special meeting and does not vote or returns a proxy with an “abstain” instruction.

If your shares are held by a broker, bank or other nominee, you should contact your broker, bank or other nominee to change your vote.

a U.S. holder of Synovus common stock from the receipt of cash instead of a fractional share of Newco common stock. You should be aware that the tax consequences to you of the merger may depend upon your own situation. In addition, you may be subject to state, local or foreign tax laws that are not discussed in this proxy statement/prospectus. You should therefore consult with your own tax advisor for a full understanding of the tax consequences to you of the merger.

For a more complete discussion of the material U.S. federal income tax consequences of the merger, as applicable, see the section entitled “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 146.

Record holders. For shares held directly, please complete, sign, date and return each proxy card (or cast your vote by telephone or Internet as provided on each proxy card) or otherwise follow the voting instructions provided in this joint proxy statement/prospectus in order to ensure that all of your shares of Pinnacle common stock or Synovus common stock, as applicable, are voted.

Shares in “street name.” For shares held in “street name” through a bank, broker or other nominee, you should follow the procedures provided by your bank, broker or other nominee to vote your shares.

Synovus shareholders: If you have any questions about the merger or how to submit your proxy or voting instruction card, or if you need additional copies of this document or the enclosed proxy card or voting instruction card, you should contact Investor Relations at (706) 641-6500 or Synovus’ proxy solicitor, Innisfree M&A Incorporated (“Innisfree”), by calling toll-free at (877) 456-3524.

The following table sets forth the basic earnings, diluted earnings, cash dividend, and book value per common share data for Pinnacle and Synovus on a historical basis and on a pro forma combined basis, for the six months ended June 30, 2025, and the basic earnings, diluted earnings and cash dividend per common share for the year ended December 31, 2024. The unaudited pro forma data was derived by combining the historical financial information of Pinnacle and Synovus using the acquisition method of accounting for business combinations, assumes the transaction is completed as contemplated and represents a current estimate based on available information of the combined company’s results of operations. The unaudited pro forma data and equivalent per share information gives effect to the merger as if the transaction had been effective on the dates presented, in the case of the book value data, and as if the transactions had become effective on January 1, 2024, in the case of the earnings per share and dividends declared data. The pro forma financial adjustments record the assets and liabilities of Synovus at their estimated fair values and are subject to adjustment as additional information becomes available and as additional analysis is performed.

The unaudited pro forma data below should be read in conjunction with Pinnacle’ and Synovus’ audited financial statements for the year ended December 31, 2024 and their respective unaudited financial statements for the six months ended June 30, 2025. This information is presented for illustrative purposes only. You should not rely on the unaudited pro forma data or equivalent amounts presented below as they are not necessarily indicative of the operating results or financial position that would have occurred if the merger had been completed as of the dates indicated, nor are they necessarily indicative of the future operating results or financial position of the combined company. The pro forma information, although helpful in illustrating the financial characteristics of the combined company under one set of assumptions, does not reflect the benefits of expected cost savings, opportunities to earn additional revenue, the impact of merger- and integration-related costs, or other factors that may result as a consequence of the merger and, accordingly, does not attempt to predict or suggest future results. The information below should be read in conjunction with “Unaudited Pro Forma Condensed Combined Financial Information” beginning on page 36.

The following unaudited pro forma condensed combined financial information and notes thereto have been prepared in accordance with Article 11 of Regulation S-X in order to give effect to the merger and the related transaction accounting adjustments (pro forma adjustments) described in the accompanying notes.

On July 24, 2025, Pinnacle and Synovus entered into an Agreement and Plan of Merger (the “merger agreement”) with Steel Newco Inc., a newly formed Georgia corporation jointly owned by Pinnacle and Synovus (“Newco”). The merger agreement provides that, upon the terms and subject to the conditions set forth therein, Pinnacle and Synovus will each simultaneously merge with and into Newco (such mergers, collectively, the “merger”), with Newco continuing as the surviving corporation in the merger and named Pinnacle Financial Partners, Inc.

Each share of common stock, par value $1.00 per share, of Pinnacle (“Pinnacle common stock”) outstanding immediately prior to the merger will be converted into the right to receive one share of Newco (“Newco common stock”) and (b) each share of common stock, par value $1.00 per share, of Synovus (“Synovus common stock”) outstanding immediately prior to the merger will be converted into the right to receive 0.5237 shares of Newco common stock. Holders of Synovus common stock will receive cash in lieu of fractional shares.

Each share of Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series D, no par value, of Synovus (“Synovus series D preferred stock”), Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series E, no par value, of Synovus (“Synovus series E preferred stock”) and 6.75% Fixed-Rate Non-Cumulative Perpetual Preferred Stock, Series B, no par value, of Pinnacle (“Pinnacle series B preferred stock”), will be converted into the right to receive one share of an applicable newly created series of preferred stock of Newco having terms that are not materially less favorable than the Synovus series D preferred stock, Synovus series E preferred stock or Pinnacle series B preferred stock, as applicable.

The unaudited pro forma condensed combined income statements for the six months ended June 30, 2025, and for the year ended December 31, 2024 combine the historical consolidated income statements of Pinnacle and Synovus, giving effect to the merger as if it had been completed on January 1, 2024. The accompanying unaudited pro forma condensed combined balance sheet as of June 30, 2025, combines the historical consolidated balance sheets of Pinnacle and Synovus, giving effect to the merger as if it had been completed on June 30, 2025.

The historical consolidated financial statements of Pinnacle and Synovus have been adjusted in the accompanying unaudited pro forma condensed combined financial information to give effect to pro forma events that are necessary to account for the merger, in accordance with U.S. GAAP. The unaudited pro forma adjustments are based upon available information and certain assumptions that Pinnacle (as the accounting acquirer) believes are reasonable. The following unaudited pro forma condensed combined financial information does not reflect the costs of any integration activities or benefits that may result from the realization of future cost savings from operating efficiencies. Certain reclassifications have also been made to align Pinnacle’s and Synovus’ historical financial statement presentation.

The following unaudited pro forma condensed combined financial information and related notes are based on and should be read in conjunction with (i) the historical audited consolidated financial statements of Pinnacle and the related notes included in Pinnacle’s Annual Report on Form 10-K for the year ended December 31, 2024, and the historical unaudited condensed consolidated financial statements of Pinnacle and the related notes included in Pinnacle’s Quarterly Report on Form 10-Q for the period ended June 30, 2025, and (ii) the historical audited consolidated financial statements of Synovus and the related notes included in Synovus’ Annual Report on Form 10-K for the year ended December 31, 2024, and the historical unaudited consolidated financial statements of Synovus and the related notes included in Synovus’ Quarterly Report on Form 10-Q for the period ended June 30, 2025, each of which is incorporated by reference herein.

The unaudited pro forma condensed combined financial information is provided for illustrative information purposes only. The unaudited pro forma condensed combined financial information is not necessarily, and should not be assumed to be, an indication of the actual results that would have been achieved had the merger been completed as of the dates indicated or that may be achieved in the future.

The merger is being accounted for as a business combination using the acquisition method with Pinnacle as the accounting acquirer, as Newco was determined to not be substantive, in accordance with Accounting Standards

Codification (“ASC”) Topic 805, Business Combinations. Under this method of accounting, the aggregate purchase consideration will be allocated to Synovus’ assets acquired and liabilities assumed based upon their estimated fair values at the date of completion of the merger. The process of valuing the net assets of Synovus immediately prior to the merger, as well as evaluating accounting policies for conformity, is preliminary. Any differences between the estimated fair value of the purchase consideration and the estimated fair value of the assets acquired and liabilities assumed will be recorded as goodwill.

The unaudited pro forma condensed combined financial information also does not consider any potential effects of changes in market conditions on revenues, expense efficiencies, restructuring, severance and retention expenses, asset dispositions, and share repurchases, among other factors. In addition, as explained in more detail in the accompanying notes, the preliminary allocation of the pro forma purchase price reflected in the unaudited pro forma condensed combined financial information is subject to adjustment and may vary significantly from the actual purchase price allocation that will be recorded upon completion of the merger.

As of the date of this registration statement, Pinnacle has not completed the valuation analysis and calculations in sufficient detail necessary to arrive at the required estimates of the fair market value of the Synovus assets to be acquired or liabilities to be assumed, other than a preliminary estimate for intangible assets and certain financial assets and financial liabilities. Accordingly, apart from the aforementioned, certain Synovus assets and liabilities are presented at their respective carrying amounts and should be treated as preliminary values. A final determination of the fair value of Synovus’ assets and liabilities will be based on Synovus’ actual assets and liabilities as of the date the merger closes (“closing date”) and, therefore, cannot be made prior to the completion of the merger. In addition, the value of the merger consideration to be paid in shares of Newco common stock upon the completion of the merger will be determined based on the closing price of Pinnacle’s common stock on the closing date and the number of issued and outstanding shares of Synovus common stock immediately prior to the closing. Actual adjustments may differ from the amounts reflected in the unaudited pro forma condensed combined financial information, and the differences may be material.

Further, Pinnacle has not identified all adjustments necessary to conform Synovus’ accounting policies to Pinnacle’s accounting policies. Upon completion of the merger, or as more information becomes available, the combined company will perform a more detailed review of Pinnacle’s accounting policies and Synovus’ accounting policies. As a result of that review, differences could be identified between the accounting policies of the two companies that, when conformed, could have a material impact on the combined company’s financial information.

As a result of the foregoing, the pro forma adjustments are preliminary and are subject to change as additional information becomes available and as additional analysis is performed. The preliminary pro forma adjustments have been made solely for the purpose of providing the unaudited pro forma condensed combined financial information. Pinnacle estimated the fair value of certain Synovus assets and liabilities based on a preliminary valuation analysis, due diligence information, information presented in Synovus’ SEC filings and other publicly available information. Until the merger is completed, both companies are limited in their ability to share certain information.

Upon completion of the merger, a final determination of the fair value of Synovus assets acquired and liabilities assumed will be performed. Any changes in the fair values of the net assets or total purchase consideration as compared with the information shown in the unaudited pro forma condensed combined financial information may change the amount of the total purchase consideration allocated to goodwill and other assets and liabilities and may impact the combined company’s statement of income. The final purchase consideration allocation may be materially different than the preliminary purchase consideration allocation presented in the unaudited pro forma condensed combined financial information.