TurboTax says I overcontributed to HSA in 2025, but I qualify for last-month rule and contributed exactly the limit

[Acasta]

TurboTax is telling me I have an excess HSA contribution of $3,419 for 2025, and I’m trying to understand why.

Here is my full situation:

2024:

• I was covered under my parents’ family HDHP for all 12 months (Jan–Dec 2024)

• I was not claimed as a dependent

• I personally contributed $4,150 to my HSA (no employer contributions)

• My Form 8889 shows:

  • Family coverage all 12 months

  • Contributions: $4,150

  • Excess contributions: $0

2025 coverage timeline:

• Jan–Feb 2025: Family HDHP coverage (parents’ plan)

• Mar–Aug 2025: No HDHP coverage (Got a job and that job's healthcare plan was not an HDHP)

• Sep–Dec 2025: Self-only HDHP coverage through my new employer

• I had self-only HDHP coverage on December 1, 2025

2025 contributions:

• Employer contributions: $173

• Personal contributions: $4127

• No spouse

What I entered in TurboTax:

• 2024 coverage: Family plan for all 12 months

• 2025 coverage:

  • Jan–Feb: Family

  • Mar–Aug: None

  • Sep–Dec: Self-only

• Spouse coverage: None for all months

• Additional income under last-month rule: $0

My understanding:
Since I had self-only HDHP coverage on Dec 1, 2025, I should qualify for the last-month rule and be allowed to contribute the full self-only limit of $4,300.

However, TurboTax says my excess contribution is $3,419.

Questions:

1. Should I qualify for the last-month rule in this situation?

2. If so, why would TurboTax still show an excess contribution?

3. Is there a specific question or screen I may have answered incorrectly?

[Opus 17]

Are you married?  What version of Turbotax are you using?  (Online or desktop?)  If Desktop, when is the last time you installed an update?

At the beginning of the season, there was a bug that created a spouse form for me, even though I am single.  After an update, I deleted all the forms, and started over, and it was fine.  

If you have not updated, do that.  Then, go to forms mode and delete form 8889-T and 8889-S (or use the remove form command online, which I think is under Tools).  Then run the HSA interview again.  If that doesn't fix it, post back here. 

[Opus 17]

Also, there are two dependent questions.

1. "Can you be claimed as a dependent by someone else?"

2. "Will the person who could claim you, actually claim you this year?"

You must answer Q1 as No.  If you can be claimed as a dependent by someone else (meet the qualifications), you are not eligible to make any contributions, even if the person who could claim you won't actually claim you.