If my total HSA contribution for 2017 was 6259 (sum of my W2s box 12d for W) why does TurboTax claim I have an excess contribution? I have a wife and kid, file jointly.
You are correct. For 2017, the maximum contribution to an HSA is $3,400 for an individual plan or $6,750 for a family plan. This is the combined contribution from both you and your employer.
First review your answers, step through the HSA interview again. An easy way to get there is to search for "hsa" (lower case) in the search box, then click the "Jump to" link in the search results.
A few common errors that usually results in excess contributions 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.
If you're within the limits but you're getting the excess HSA contribution message, it's most likely because you're not eligible or you answered the eligibility questions incorrectly or didn't get a chance to answer them at all. To recap, the HSA eligibility requirements are:
You must be enrolled in a high deductible health plan (HDHP).
You can’t be enrolled in Medicare or another secondary health insurance policy.
You can’t be claimed as a dependent on somebody else's return.