Deductions & credits

Per the IRS, ""Your qualifying child must have a valid SSN issued on or before the due date of your return (including extensions)" and further: "If your social security card reads “Valid for work only with INS authorization” or “Valid for work only with DHS authorization,” you have a valid SSN, but only if that authorization is still valid."

As the instructions read that you need a valid SSN before the due date of the return, if you have a valid extension filed for your federal return, AND you were able to get a valid SSN for your son (meaning it states it is valid for work only with INS or DHS authorization AND that authorization is currently valid as of the date you file your return AND you file your return on or before the due date of your extended return) then you should qualify for those benefits.

I cannot find an IRS reference specific to the situation where the child's work status has changed, but there is a reference to the timeline in IRS Publication 596 that states:

• If an SSN for you or your spouse is missing from your return because either you or your spouse didn't have a valid SSN on or before the due date of your 2023 return (including extensions) and you later get a valid SSN, you can’t file an amended return to claim the EIC. However, if you or your spouse were issued an SSN that wasn't valid for the EIC, but by the due date of your 2023 return (including extensions) you or your spouse became eligible for a social security card without "Not valid for employment" printed on it, you may claim the EIC on an original or amended 2023 return even if the social security card wasn't updated by the due date of your 2023 return (including extensions).

Based on the above references, it would seem that if your child receives DHS authorization to work prior to the due date of the return (including extensions), then you would be able to claim these tax benefits on an original or amended tax return that is filed prior to the due date.  However, once the due date of your tax return has past, you are not eligible to file an original or amended return to claim the benefits.