Since I cannot see your tax return, I can only make suggestions on what is happening and how you can address the situation.
As you correctly deduce, you should have a carryover only if two things happened in 2017:
- you made excess contributions to the HSA in 2017, and
- you did not withdraw the excess before the due date of the return.
You say that you did not have excess contributions in 2017 and that the $4,819 was the code W amount in box 12 on your W-2.
Please look at your 2017 return at form 5329, Part VII, line 48. Is there a number here? This would be the penalty in 2017 for excess HSA contributions that were not withdrawn before the due date of the return.
If you did not have an amount on line 48 on the 5329, is it possible that in one of your iterations of doing the 2017 return, that you did see the excess contribution message but subsequently fixed it? Perhaps the carryover lagged behind.
On your 2017 form 8889, on lines 12A, 12B, and 12C (this is as seen in TurboTax Forms mode), are there any numbers here? 12A is the excess HSA contributions made through the employer, 12B is the amount of the excess withdrawn before the due date of the return, and 12C is the amount of the excess carried over to 2018. If there was no excess in 2017, then all three numbers should be blank.
On your 2017 form 5329 (if one), is there a number in line 46? This would be a carryover from 2016 to 2017, which could have triggered an excess in 2017 if you had not reduced your 2017 contribution level. Yes, I am grasping at straws here.
You have obviously investigated this, and if the fields on 12A, 12B, and 12C are blank, then I can have no explanation for why you see an amount in line 11a in the 2018 Carryover Wks.
