You had the choice of opting out of the 2021 CTC advance payments if you didn’t want to roll the dice that you would be entitled to the full amount when you file your 2021 tax return, or if you wanted to claim the full 100% of the credit on your 2021 tax return for some other reason. The IRS provided a “CTC Update Portal” online for this purpose, but you would have had to have opted out before the payments ended in December 2021.