The CTC is an annual tax credit. Taxpayers with dependent children only can avail this. It was introduced by the Taxpayer Relief Act of 1997.  As per the revised qualification criteria, for the tax year 2021, you can avail of the credit if your modified adjusted gross income is below $75,000 if you are a single filer. This maximum limit of the modified AGR is fixed at $150,000 for married & joint filers and $112,500 for heads of household respectively.