The statutory deadline for contributing to your HSA is through the un-extended deadline for filing your income tax return. Normally, that’s the April 15 after the close of the tax year. However, for the 2021 income tax, you may file Form 1040 or 1040-SR by April 18, 2022. The due date is April 18, instead of April 15, because of the Emancipation Day holiday in the District of Columbia – even if you don’t live in the District of Columbia. If you live in Maine or Massachusetts, you have until April 19, 2022, because of the Patriots' Day holiday in those states. If you were serving in, or in support of, the U.S. Armed Forces in a designated combat zone or contingency operation, you may be able to file later. See Pub. 3 for details. Thus, you may contribute to your 2021 HSA through April 18, 2022, April 19, 2022 (if you live in Maine or Massachusetts), or some other date (if you served in a designated combat zone or contingency operation).