About

About HSAProrate

A free, no-sign-up calculator for the question employers and HSA custodians rarely answer clearly: exactly how much can you contribute when you were not HDHP-eligible for the whole year?

HSA contribution limits sound simple until your coverage starts or ends mid-year. Then the rules layer up: the limit is prorated by the months you were eligible (eligibility is decided on the 1st of each month), the age-55 catch-up prorates too, and the last-month rule lets you skip proration entirely if you are eligible on December 1 — at the cost of a 13-month testing period that can claw the extra back, with a 10% penalty, if you lose eligibility. HSAProrate runs all of that and shows you the number plus exactly how much is at risk.

How it works

It applies the response-side math of IRS Publication 969 and Form 8889: monthly proration of the annual limit and the catch-up, the last-month rule, and the testing-period dates and clawback. Everything runs in your browser — nothing you enter is sent or stored.

What it is not

It is a general estimate for one person, not tax advice. The HSA limit is the combined total of your and your employer’s contributions; couples share the family limit; and figures change every year. Confirm the current numbers with the IRS or a tax professional before you act.