Interesting that I haven't seen this come up before. I've confirmed with testing that TurboTax does not properly allow the full family contribution limit if you change from family coverage to single coverage after making the HFD.
As a workaround, indicate that you had family HDHP coverage for the entire year.
@MaryK4 , you might want to report this bug to the Product Qualify group. However, I suspect that since there is a workaround for this uncommon situation, this bug will not get much, if any, attention by the developers.
