has anyone experienced doubling of box 12 code w resulting in the system thinking I overfunded my HSA

[dmertz]

Make sure that in the HSA section you have not entered the code-W amount as personal contributions.  Amounts reported with code W are considered to be employer contributions, even when made by payroll deduction.  Enter amounts shown in box 12 of your W-2 only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax.

[BillM223]

In the HSA interview, there is a screen titled "Let's enter [name]'s HSA contributions". It has two lines: the top one shows you the code W amount from your W-2, and the bottom one is where you enter your "personal" contributions. 

"Personal" confuses most taxpayers. It refers to contributions made by you directly to the HSA, NOT through your employer. Do NOT enter any part of the code W amount on this second line. Don't worry, once your contribution is in the Code W amount, you will get "credit" for the contribution. 

This is a common reason why HSA contributions are doubled.