My husband's self- plan HSA changed to family-plan last 3 months which is prorated higher. He stayed well within the max contribution. I think Turbotax is confusion my own self-pay with his family plan.
No, what is confusing is the rules by which the annual HSA contribution limit is calculated.
Please explain why "self-pay" means. Did you also have HDHP coverage under a Self-only HDHP policy?
I can't be sure, but it may be that when your spouse went on Family coverage, that you two did not realize that your Self-only policy stopped counting for determining the annual HSA contribution limit.
That is, when you go on to a Family HDHP plan, then the two spouses share the (in 2024) $8,300 limit. It is NOT that one spouse gets $8,300 and the other gets $4,150.
Please let us know if you stayed under your own HDHP Self-only plan.
If you did not, then please tell us your details: what kind of HDHP plan, how many months, which months, and how much you two (and any one else) contributed.