AMARIN CORP PLC\UK Income Taxes Disclosure

The Company recognizes interest and penalties related to uncertain tax positions within the provision for income taxes. The total amount of unrecognized tax benefits that would affect the Company’s effective tax rate if recognized is $10.8 million and $11.7 million as of December 31, 2025 and 2024, respectively. The Company recognized interest related to uncertain tax positions of $2.1 million and $1.7 million for the years ended December 31, 2025 and 2024, respectively. No penalties have been recognized in conjunction with these positions.

The Company does not expect any gross liabilities to expire in 2026 based on statutory lapses or audits.

The Company is subject to a corporate tax rate in Ireland of 25% for non-trading activities and 12.5% for trading activities. For the years ended December 31, 2025, 2024, and 2023, the Company applied the statutory corporate tax rate of 25% for Amarin Corporation plc, reflecting the non-trading tax rate in Ireland. However, for Amarin Pharmaceuticals Ireland Limited, a wholly-owned subsidiary of Amarin Corporation plc, the Company applied the 12.5% Irish trading tax rate. In the table above, the Company used Amarin Corporation plc’s 25% tax rate as the starting point for the reconciliation since it is the parent entity of the business.

In April 2016, the Company adopted ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Share-Based Payment Accounting which changes the accounting for certain aspects of share-based payments to employees. One aspect of the standard requires that excess tax benefits and deficiencies that arise upon vesting or exercise of share-based payments be recognized as an income tax benefit and expense in the income statement. Previously, such amounts were recognized as an increase and decrease in additional paid-in capital. This aspect of the standard was adopted prospectively, and accordingly the provisions for income taxes for the years ended December 31, 2025, 2024 and 2023 includes $0.2 million, $1.0 million and nil of excess tax benefits, respectively, arising from share-based payments during the period.

The Company assesses whether it is more likely than not that the Company will realize its deferred tax assets. The Company determined that it was more likely than not that the net operating losses and the related deferred tax assets would not be realized in future periods and a full valuation allowance has been provided for all periods.

During 2025, the Company recorded adjustments to its deferred tax accounts related to the impact of foreign exchange rate changes and to reconcile the financial statement accounts to the amounts expected to result in future income and deductions under local law, primarily as it relates to Irish net operating losses and deferred taxes for stock compensation. These adjustments were fully offset with valuation allowances based on the Company’s position with respect to the realizability of its recorded deferred tax assets.

The Company has combined U.S. and non-U.S. net operating loss carryforwards of $1.0 billion, which do not expire. The total net operating loss carryforwards decreased by approximately $8.9 million from the prior year primarily as a result of adjustments to reconcile to the amount reported on the filed 2024 foreign tax returns. In addition, the Company has U.S. Federal tax credit carryforwards of $8.7 million and state tax credit carryforwards of $3.3 million. These amounts exclude the impact of any unrecognized tax benefits and valuation allowances. These carryforwards, which will expire between 2026 and 2044, may be used to offset future taxable income, if any.

As of December 31, 2025, there are no earnings that have been retained indefinitely for reinvestment by foreign subsidiary; therefore, no provision has been made for income taxes that would be payable upon the distribution of such earnings or the recovery of the Company’s investment in its subsidiaries as the amount of the related unrecognized deferred income tax liability is zero.

The Company's and its subsidiaries' income tax returns are periodically examined by various tax authorities. The Company is currently under audit by the IRS for tax years 2021 to 2023 and by the New York Department of Finance for the years 2018 and 2019. Although the outcome of tax audits is always uncertain and could result in significant cash tax payments, the Company does not believe the outcome of these audits will have a material adverse effect on the Company's consolidated financial position or results of operations.