After you file

You can, but the PATH Act made several changes to the tax law, including preventing retroactive claims of the EITC and CTC by amending a return or filing an original return for any earlier year in which the individual or anyone listed on the return did not have a SSN valid for employment.  You can't claim EITC or CTC unless the Social Security number for you, your spouse (if married filing a joint return) or a qualifying child is issued before the due date of the return including any valid extensions.