There are two possibilities: one is that you did not enter the months you were covered and the other is that TurboTax automatically applied the last-month rule to make you eligible for the maximum contribution.
To enter the months you were covered:
- Go to Federal > Wages & Income > Less Common Income > 1099-SA, HSA, MSA and click Start/Revisit.
- Make sure you have HSA selected.
- Enter your withdrawals from your HSA by answering Yes to Did you use your HSA to pay for anything in 2021?
- Assuming you did not inherit this HSA, select No.
- Under Let's enter your HSA contributions your employer amount should already be in there from the W-2.
- Did your employer tell you about any other contributions? Answer No.
- Answer the questions on the next two screens, making sure you answer the question related to your HDHP correctly.
- However, if you were covered on December 1, 2021, you are considered covered the whole year, and therefore there is no excess contribution. This is true as long as you maintain HDHP coverage for the testing period through the end of 2022. Otherwise, you will have to pay for the excess contribution on your 2022 return.
If you did not know about the last-month rule, it is not too late to make an out-of-pocket contribution to your HSA for 2021 which will reduce your taxable income. Just make sure if you do decide to do this, you make sure it is marked as a 2021 contribution, not 2022.
