I assume that you are referring to the question in the HSA interview, "Did you overfund your HSA in 2017?"
The Help link on this screen asks "How can I figure out if I overfunded my HSA". When you click on this link, you see "Check your 2017 year tax return and look for Form 5329. If the form is there and you see an amount on line 48, your HSA was overfunded and you should answer Yes."
When you say "What if I cannot find if I overfunded HSA", I have to wonder whether you mean that you don't have a 5329 on your 2017 return or if you don't have a copy of your 2017 return.
If you don't have a 5329 on your 2017, the answer "No" to the overfunding question and continue with the HSA interview.
If you don't have your 2017 return, then let me explain what is happening and see if that jogs your memory.
The question about overfunding your HSA in 2017 really isn't about whether you made excess contributions to your HSA in 2017, it's about whether you carried over any excess contributions from 2017.
If you did not make excess contributions in 2017, then answer "No" and continue.
If you did make excess contributions in 2017, but withdrew them all before the due date of the return, then answer "No" and continue.
If you received a 1099-SA with the distribution code of '2' and there is an amount in box 1 that is equal to the total amount that was excess in 2017, then answer "No" and continue.
You only answer "yes" if there was an excess in 2017 and you didn't withdraw all of it.
If you think that this may be possible, you need to find out what that carryover is. This is because the carryover will be counted as a personal contribution in 2018, and it and your other contributions in 2018 need to be less than or equal to your current annual HSA contribution limit (or else you have another excess).
If the problem is that you are missing your 2017 return, then you can get a Transcript from the IRS.
You can order a Tax Return Transcript from the IRS. This is not a copy of a return, but it shows most line items including your adjusted gross income (AGI) from your original tax return (Form 1040, 1040A or 1040EZ) as filed, along with any forms and schedules. It doesn’t show changes made after you filed your original return.
Taxpayers often use the information from transcripts to file prior year returns, when the original paperwork is lost. The transcripts are free and with luck, you can get them online.
Please look at the IRS website for Transcripts at https://www.irs.gov/individuals/get-transcript .
