I have the same issue. I plugged the numbers in using TurboTax online, but it didn't calculate correctly, showing $402. I found out with a letter from the IRS today, stating the amount was miscalculated and that I owe an additional ~$1400, on top of the ~1300 mailed in on tax day. I didn't manually calculate everything on my tax forms to verify the amounts before I eFiled, as I trusted TurboTax to do that correctly. Looking at the printed 1040, I can easily spot the error. I owe it fair and square, it's just irritating having to rehash 2020 taxes and pay more. To make things more weird, I received a Treasury check for almost $300. The note on the check says it's for some stimulus money I was supposed to receive.
