The Child Tax Credit (CTC) and Additional Child Tax Credit (ACTC) help ease the financial burden of families with children. This paper provides taxpayer and dollar participation estimates for the CTC and ACTC covering tax year 2021. In this tax year the credit was temporarily expanded under the American Rescue Plan Act. The estimates derive from linking the 2022 Current Population Survey Annual Social and Economic Supplement (CPS ASEC) to IRS administrative data. This approach, called the Exact Match, uses survey data to identify CTC/ACTC eligible taxpayers and IRS administrative data to indicate which eligible taxpayers claimed and received the credit. Overall, in tax year 2021, eligible taxpayers participated in the CTC and ACTC program at a rate of 91 percent while dollar participation was 85 percent.