The Illegal War Refund Act would require the federal government to compensate U.S. taxpayers and their dependents for the economic costs of an Iran war by making annual payments starting in fiscal year 2027. Each year, the Office of Management and Budget would calculate the total economic costs to taxpayers from the war, including expenses related to interest rates, fuel prices, food prices, and inflation. The Treasury Department would then transfer funds from the Department of Defense's unobligated budget accounts to pay eligible individuals, with each taxpayer and dependent receiving an equal share of the calculated amount. Payments would be distributed by October 30 of each fiscal year to any individual who filed a tax return in the preceding year, plus their dependents, though the payments cannot include the names or signatures of elected officials. The bill does not specify the dollar amount of payments or how long the program would continue, leaving those details to be determined by annual calculations.