we can't see your returns or notices. if you don't understand what's going on we have a much harder time because of this. try contacting the tax advocate for a clear explanation.
your other choices
view a transcript of your 2019 return which would show as filed and as adjusted by the IRS
https://www.irs.gov/individuals/get-transcript
pay a tax pro to go over all your documents and notices.
or use a service provided by a Turbotax partner
The Audit Defense service is provided by TaxResources, Inc., also called TaxAudit.com, in partnership with TurboTax. If you paid for Audit Defense and you received an IRS notice, call TaxResources, Inc. at 877-829-9695, or report your IRS notice on their website at http://intuit.taxaudit.com/.
this is a wild guess.
the form missing from your return was Form 8962 Premium Tax Credit (Obamacare). the information to complete it comes from Form 1095A Health Insurance Marketplace Statement. The 8962 computes the allowable amount of advance premium tax credits (PTC) and the amount that has to be repaid. If you left this form off your return and were required to pay back some of those credits as shown on line 29 you owe that amount. if you owe this would likely lower any deduction on Schedule 1 for self-employed health insurance but possibly increase the QBI deduction on line 10 of form 1040. omitting the form can affect the amounts on other lines and thus change the amount of the taxes you owe.
y
