I received a 1095-A and entered the information into my return. My return exploded and now I owe all the money for insurance back? $26500!! Where will this ever be deductible as health ins premiums? Can I do it now?
I think you're saying that your repayment is on this year's -- your 2018 -- return.
If that's the case you can deduct the repayment, but it'll need to be claimed on your TY 2018 return -- the one you file next year..
Any amount of advance payments of the premium tax credit that you have to pay back can be included in medical expenses for that same year when you itemize deductions.
Please see "Premium Tax Credit" in IRS Publication 502, Medical and Dental Expenses for more information.