For new HSAs, are maximum contributions prorated on a monthly basis?

For new HSAs, are maximum contributions prorated on a monthly basis?: Annual HSA contributions for new HSAs are not prorated on a monthly basis as long as you are HSA- eligible on December 1 and maintain HDHP coverage throughout the subsequent 13-month testing period. The testing period begins on December 1 in the year the qualified HDHP coverage is obtained and runs through December 31 of the following year. The testing period is also called the “13-month rule.” Enrolling in an HDHP and establishing an HSA any time after January 1 triggers the “testing period” if you contribute the maximum amount to your HSA. If you do not satisfy the 13-month rule, contribution limits are prorated and tax consequences apply. See Chapter 5, Section 1.2 on page 37 for examples of pro-rated maximum contribution amounts.