ICON PLC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 20-F

(Mark One)

☐ Registration statement pursuant to Section 12(b) or (g) of the Securities Exchange Act of 1934

OR

☒ Annual report pursuant to Section 13 or 15 (d) of the Securities Exchange Act of 1934

For the fiscal year ended: December 31, 2025

OR

☐ Transition report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

OR

☐ Shell company report pursuant to section 13 or 15(d) of the Securities Exchange Act of 1934.

Commission File Number:333-08704

ICON PUBLIC LIMITED COMPANY

(Exact name of Registrant as Specified in its Charter)

ICON PLC

(Translation of Registrant’s name into English)

Ireland

(Jurisdiction of Incorporation or Organization)

South County Business Park, Leopardstown, Dublin 18, D18 X5R3, Ireland.

(Address of principal executive offices)

Nigel Clerkin, Chief Financial Officer

South County Business Park, Leopardstown, Dublin 18, D18 X5R3, Ireland.

Nigel.Clerkin@iconplc.com | +353-1-291-2000

(Name, telephone, email and/or facsimile number and address of Company contact person)

Securities registered or to be registered pursuant to Section 12(b) of the Act:

Indicate the number of outstanding shares of each of the issuer’s classes of capital or common stock as of the close of the period covered by the annual report:76,567,325 Ordinary Shares.

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes☐ No ☒

If this report is an annual or transition report, indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. Yes☐ No ☒

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or an emerging growth company. See definition of “large accelerated filer, "accelerated filer,” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer ☒ Accelerated filer☐ Non-accelerated filer☐

Emerging growth company☐

If an emerging growth company that prepares its financial statements in accordance with U.S. GAAP, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included

in the filing reflect the correction of an error to previously issued financial statements.☒

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive- based

compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b).☒

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing:

U.S. GAAP ☒ International Financial Reporting Standards as issued Other☐

by the International Accounting Standards Board☐

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow. Item 17☐ Item 18☐

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act) Yes☐ No☒

EXPLANATORY NOTE

Overview

As described in our Report on Form 6-K furnished on April 29, 2026, the Audit Committee of the Board of Directors (the “Audit Committee”), after discussion with management of the Company, concluded on April 27, 2026, that the Company’s previously issued audited financial statements included in its Annual Reports on Form 20-F for the years ended December 31, 2024 and 2023 (the “Affected Audited Periods”) and the unaudited interim financial statements included in the Company’s Current Reports on Form 6-K for the quarterly periods ending on and falling between September 30, 2025 and March 31, 2023 (the “Affected Unaudited Periods” and together with the Affected Audited Periods, the “Restated Periods”) should no longer be relied upon.

In this Annual Report on Form 20-F (this “Form 20-F”) for the year ended December 31, 2025, we are restating the consolidated financial statements for the Affected Audited Periods, that were previously reported in our Annual Reports on Form 20-F for the years ended December 31, 2024 and 2023.

Accordingly, this filing includes more information than would normally be included in an Annual Report on Form 20-F in order to provide a composite presentation of information for the Affected Audited Periods.

In addition to the consolidated financial statements and related information for the year ended December 31, 2025, this Form 20-F includes the following (collectively, the “Restatement"):

•the restated Consolidated Balance Sheets at December 31, 2024 and December 31, 2023, and

•the restated Consolidated Statements of Operations, Consolidated Statements of Comprehensive Income, Consolidated Statements of Shareholders’ Equity and Consolidated Statements of Cash Flows for the years ended December 31, 2024 and 2023.

For additional information, see Note 1A, Restatement of Previously Issued Consolidated Financial Statements to the consolidated financial statements included in this Form 20-F.

This Form 20-F also includes additional information regarding the Affected Audited Periods, including in Item 5. Operating and Financial Review and Prospects.

We intend to restate the financial statements for the Affected Unaudited Periods through an amendment to our Current Report on Form 6-K originally filed with the U.S. Securities and Exchange Commission (“SEC”) on October 23, 2025. The Company does not intend to separately amend other filings that were previously filed with the SEC.

Conclusion of Investigation

As previously disclosed, in October 2025, the Audit Committee initiated an investigation into certain accounting practices and controls, following concerns reported to the Audit Committee through Company management. The Audit Committee promptly engaged outside legal counsel, who were supported by forensic and technical accounting firms, to conduct the investigation (the “Investigation”) and notified the Company’s independent registered public accounting firm. The Company has also self-reported the matter to the SEC and other relevant agencies. The Investigation primarily focused on revenue recognition practices, and, in connection with the Investigation, the Company has determined that improper adjustments were made to the clinical trial services revenue of the Company from the third quarter of 2023 to the fourth quarter of 2024. The Company also identified errors in determining the estimated cost to complete, the assessment of realizable value, and certain manual adjustments in respect of clinical trial services revenue contracts during 2023, 2024 and 2025. The Audit Committee concluded that the Company’s previously issued consolidated financial statements for the Restated Periods should no longer be relied upon and that such financial statements required restatement. As described in this Form 20-F, the Company is restating its consolidated financial statements for the Restated Periods.

Restatement of Financial Statements

The restated financial statements as of and for the years ended December 31, 2024 and 2023 correct the following errors (the “Restatement Errors”):

•A $92.7 million overstatement of revenue for the year ended December 31, 2024 and a $65.3 million overstatement of revenue for the year ended December 31, 2023. Included in the revenue overstatements are errors of $73.6 million and $68.9 million for the years ended December 31, 2024 and 2023 respectively. These errors relate to improper adjustments recorded to recognize revenue outside of normal system processes for long-term clinical services revenue contracts, errors in determining the estimated cost to complete, the assessment of realizable value, and certain manual adjustments in respect of certain long-term clinical services revenue contracts. Also included in the revenue overstatements are errors of $19.1 million overstatement and $3.6 million understatement for the years ended December 31, 2024 and 2023 respectively.

•An overstatement of unbilled revenue and unearned revenue in respect of right of offset, as at December 31, 2024 and December 31, 2023 of $192.4 million and $100.8 million respectively due to certain contract assets and liabilities with a legal right of offset not being identified.

•A $13.1 million overstatement of income tax expense for the year ended December 31, 2024 and a $6.6 million understatement of income tax expense for the year ended December 31, 2023.

In addition to the errors described above, the Restatement also includes adjustments to correct certain other immaterial errors, consisting of adjustments to reclassify certain balance sheet accounts and immaterial adjustments to record previously unrecorded adjustments including those identified in audits of prior years’ financial statements (the “Other Adjustments”).

The impact of the Restatement on the Consolidated Statements of Operations is shown below. For additional information, see Note 1A, Restatement of Previously Issued Consolidated Financial Statements to the consolidated financial statements included in this Form 20-F.

The Restatement Errors on the Balance Sheets at December 31, 2024 and December 31, 2023 represent 1.4% and 0.7% of Total Assets / Total Liabilities and Shareholders’ Equity in each of the years, respectively.

The Restatement does not affect cash flows or net debt.

Internal Control Considerations

In connection with the Restatement, management has evaluated the effectiveness of the Company’s disclosure controls and procedures and internal control over financial reporting as of December 31, 2025 and has determined they were not effective due to the material weaknesses described in Part II Item 15. Controls and Procedures. Management is taking steps to remediate the material weaknesses identified in our internal control over financial reporting as described in Item 15. Controls and Proceduresof this Form 20-F.

TABLE OF CONTENTS

PART I

PART II

PART III