You misunderstand the contribution limit rule for a family. The max is $8550, split any way you want between the two of you. The excess + earnings will need to be withdrawn by 4/15/2026. Nrmally the max your spouse could contribute 1/2 year both types is $4300/2 + $8550/2 = $6425. However, there is a special rule that if a person is covered by a family plan on 12/1, they can make a full year's family plan contribution. That's how she was able to make the $8550 contribution
Since the contribution to her HSA was based on her being an eligible (family plan) individual for the entire
year under the last-month rule, she must remain an eligible individual (covered by a family plan) during the testing period. The testing period begins with the last month of your tax year and ends on the last day of the
12th month following that month (for example, December 1, 2025, through December 31, 2026). If she fails to remain an eligible individual (family plan) during the testing period, for reasons other than death or becoming disabled, she will have to include in income the total contributions made to her HSA that wouldn’t have been made except for the last-month rule. This amount is income in the year in which she fails to be an eligible
individual. This amount is also subject to a 10% additional tax. The income and additional tax are calculated on Form 8889, Part III.
You have the right to withdraw the excess from either plan; however, the safest approach would be to withdraw from her HSA. Thus, the last month rulle would not apply to her account.
