This bill, titled the "End Tax Penalties on American Hostages Act," amends the Internal Revenue Code of 1986 to offer significant tax relief to United States nationals who are unlawfully or wrongfully detained or held hostage abroad. It establishes that the period during which an individual is detained or held hostage will be disregarded for determining tax deadlines, interest, penalties, and credits or refunds. This provision also extends to the spouse of the detained individual, ensuring comprehensive support for affected families. The legislation defines "applicable individuals" as U.S. nationals identified as unlawfully detained by the Secretary of State or as hostages by the Hostage Recovery Fusion Cell. These entities are required to provide annual lists of such individuals to the Treasury Department. The Treasury must then update its systems to suspend collection activities and abate or refund any interest or penalties assessed against these individuals prior to their official identification as detained or hostage. Furthermore, the bill creates a program for retroactive relief, allowing "eligible individuals" to apply for refunds or abatement of penalties and interest paid between January 1, 2021, and the bill's enactment date. The Secretary of State and Attorney General will compile lists of these individuals, and the Treasury will notify them of their eligibility. To facilitate these refunds, the bill extends the statute of limitations for claims and waives certain other limitations, ensuring that affected individuals can recover previously paid amounts.