In most cases, your HSA contribution has already been reported in Box 12 of your W-2 with code W: Employer Contributions to Health Savings Account.
Despite the misleading name, code W reports both your and your employer's contribution. (If you think the name is confusing, think of it as just "Contributions to Health Savings Account".)
A common error that usually results in excess HSA contributions, which are taxable with a penalty, is if you, on the Let's enter your HSA contributions screen, accidentally duplicated the amounts already reported in the first line, contributions from Box 12 of your W-2.
For example, if you have $3650 on your W-2, Box 12 (Code) and also entered $3650 separately on the Let's enter your HSA contributions screen, that would equal $7300 which is $550 over the maximum allowed HSA contribution for a family plan ($6750). This results in the Form 5329 (Additional Taxes).
This should remove Form 5329 generated by the above-described error.
Double check your W-2. If you have an entry in Box 12 with a code W, then go to the HSA Contribution screen delete the entry, unless you made other HSA contributions besides through your work.
Please follow the instructions below for editing your HSA contributions below if you are using TurboTax Online (except Home & Business version):
1. Click on Federal
2. Click on Deductions & Credits
3. Look in your list for HSA, MSA Contributions and go to step 6; otherwise, continue to step 4
4. Click on Jump to full list
5. Click Show more next to Medical
6. Click Start/Edit next to HSA, MSA Contributions
7. Follow through the prompts, when you get to the screen that says Enter Your HSA Contributions, you can put additional contributions made after-tax from your own funds (take-home pay, savings, etc.) as All Other Contributions.
8. This page will automatically pull in your W-2 contributions from you and your employer that were pre-tax.
9. Complete the rest of the related interview questions
