That previous answer is wrong. The new child tax credit doesnt refer to 2020 there for the answer is misleading. The new child tax credit refers to 2021 and temporarily increase the amount from 2000 to 3600 for kids under 6 and 3000 for kids under 17. The question remains. Will the check be sent out automatically for the difference if you have already filed, or will you have to wait until 2022 to file and receive it.
