I agree this is TT's fault.
We had very similar issues and received an IRS letter dated 9/6 demanding $650 + $6.01 in interest charges back to the date we filed. TT should have known and calculated correctly since our income didn't vary much at all from 2019 to 2020 and all stimulus funds were correctly reported. The difference is in the payments and credits, which IRS calculates differently than TT, buy $650 in IRS' favor.
