This is how it is handled in layman's terms ... I could site the IRS rules and instructions however your head will probably explode ... I have been doing taxes and teaching the tax courses for more than 25 years so here is the answer again ...
If you had to pay back the 2018 advance credit that payback goes on the 2018 return which then allows an adjustment to income for the SE health Insurance deduction depending on the income from the SE ... any unallowed deduction is then moved to the Sch A by the program automatically to be used only if you itemize deductions. NOTHING is reported on the 2019 return ... that is how the rules are written for this situation. Review the 2018 return ... did the program calculate it correctly ? If not you need to amend the 2018 return.
