If you cannot claim the entire amount of your child tax credit because it exceeds your tax, don’t be discouraged, because you may be able to claim the unused portion as an additional child tax credit. The additional child tax credit is a refundable credit, and is available to you whenever you cannot claim the entire amount of the child tax credit.
The amount of the refund, however, may differ depending on your total earned income. It may also be affected by the amount of Social Security and Medicare taxes that were paid.
Figuring and Claiming the Credit: