The stimulus checks were based on your 2019 return. However, when you filed your 2020 with both children, the additional amount would have been added. Per the IRS Q&A, " If we have not processed your 2020 tax return when we determine the amount of your advance Child Tax Credit payment for any month starting July, we will estimate the amount of your 2021 Child Tax Credit based on information shown on your 2019 tax return (including information you entered into the Non-Filer tool on IRS.gov in 2020). Once we have processed your 2020 return, we will recalculate your advance Child Tax Credit payments and adjust any remaining monthly payments."
Nick K, EA
