@wendy3152020
I want to recap here.
Wife is eligible to contribute to an HSA if she is enrolled in an individual or family HDHP and has no "other coverage" that disqualifies the wife. The husband's FSA counts as "other coverage", since it can be used to pay the expenses of the husband or the wife. You first need to determine when the FSA ends.
IRS allows a maximum grace period to use up the funds of 2-1/2 months. So coverage by the FSA must end no later than March 15, or whenever the funds are used up, whichever comes first. Even if the account is locked and claims can't be submitted until later, you are not allowed to submit any claim that occurred after the end of the grace period (March 15). In other words, if the account is locked and you can't submit a claim until after April 1, you could still only submit a claim that was paid before March 15. A claim after March 15 should be denied by the FSA administrator. On the other hand, if you have enough expenses in January to use up the FSA, then it ends in January even if you can't submit the claim until later.
Your eligibility to contribute to an HSA is determined by your medical coverage on the first day of each month. That determines the total amount you are eligible for the year, but it does not matter when in the year the contributions are made. It's ok to make contributions in January or February even if you still have the FSA, as long as your overall total for the year is not more than your limit.
The family coverage limit for 2025 is $8550, or $712.50 per month, so using the standard rules, if the FSA coverage extended to March 15, your limit for 2025 would be 9 months x $712.50 = $6412.50.
Yes, you can use the last month rule. If you are eligible on December 1, 2025 and plan to remain eligible for all of 2026, you can contribute the full amount of $8550 for 2025.
