@bobby42 You seem to be mixing up the Child Tax Credit and the Recovery Rebate Credit. They are two completely different credits. The $4,200 amount looks like the Recovery Rebate Credit, $1,400 per person for 3 people, not the Child Tax Credit. The maximum Child Tax Credit is $3,000 for each child age 6 through 17 at the end of 2021, or $3,600 for each child age 5 and under.
The advance payment of the Recovery Rebate Credit was called an Economic Impact Payment (EIP) or stimulus payment. It was paid in a single lump sum in most cases, and there was no way to opt out.
The monthly payments that you opted out of were for the Child Tax Credit, not the Recovery Rebate Credit.
You need to be clear about which credit you are looking at. You have to tell TurboTax how much you received in advance for each credit separately. The calculation of both credits is based on your 2021 tax return, but the advance payments were based on your 2020 tax return, or possibly even 2019.
Do not, under any circumstances, tell TurboTax that you received a payment that you did not actually receive. Enter only the payments that you actually received, if any, for each of the two credits.
