Client is married filing joint with two kids, 15 and 19 (full time student).  No errors and I e-file.  IRS rejects. Efiling log Error Detail says "Each dependent in the Dependent Detail on the return with Eligible for Child Tax Credit checked must be under the age of 17.  You may be eligible to claim the Credit for other Dependents if you meet the requirements."  Error Resolution says check name, ssn, birth date, relationship.  All are correct. I believe messaging on the reject mentioned an income limit of $4300 but upon a little research, that is the cap for Other Dependent, not a limit on qualifying child.

I ask the tax payer if his kids worked.  Yes, both filed tax returns, didn't claim dependency.  I end up removing the 19 yr old from the return, amend his return claiming dependency and taking education tax credit.  That worked out okay.

I efile the return again with just the 15 yr old and it rejects again.  Same messaging.  Only when I check the box taking the child as Other Dependent will it accept, but the taxpayer missed out on $1500 of a tax credit.

What did I do wrong?  What am I missing here?