If you are not eligible for the third stimulus payment based on your 2021 tax return, you do not have to enter the amount from the IRS letter. If you are married filing jointly you are not eligible if your 2021 AGI is $160,000 or more. In that case, TurboTax doesn't ask whether you received the payment because it doesn't matter whether you received it or not. The purpose of asking about the payment you received is to determine whether you are entitled to a Recovery Rebate Credit on your 2021 tax return. Bur if your AGI is over the maximum, you cannot get the Recovery Rebate Credit in any case, so there is no need to ask whether you received the payment. Form 1040 line 30 should be blank.
You can keep the payment that you received. You do not have to pay it back.
