saving-for-retirement

HSA Last-Month Rule — Make a Full-Year HSA Contribution Even If You Weren't Eligible All Year

Difficulty Medium Risk Medium Applies To All Potential Savings Allows a larger HSA contribution than pro-rating would otherwise permit Last Verified 2026-04-03

HSA Last-Month Rule — Make a Full-Year HSA Contribution Even If You Weren’t Eligible All Year

What Is It?

The HSA last-month rule can let a taxpayer who is HSA-eligible on December 1 make the full-year contribution instead of a prorated amount.

What Most People Don’t Know

  • The testing period is the real trap.
  • Failing the testing period can trigger income inclusion and an extra tax.
  • This is one of the fastest ways to increase a late-year HSA contribution.

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