My son is 25 year old full time student. As per IRS Child Test, he does not qualify as a dependent as he is over 24. However, in Turbo Tax marked him as dependent.

[ajartax]

My son is 25 year old full time student. As per IRS Child Test,  he does not qualify as a dependent as he is over 24. However,  in Turbo Tax ->  Personal Info -> Dependents  interview questions,  Turbo Tax determined him as a Dependent as his income is less than $4,400, he is full time student, lived with me whole year, unmarried. 
Question - why does Turbo Tax fail age test?  

[Bsch4477]

There are two classifications for dependency. The one your son fits is called qualifying relative. For that age is irrelevant as long as you provide more than half of his support, he earned less than $4,400 and he lived with you. Temporary absences  from home at school count as living with you. 

[DawnC]

He is a qualifying relative (no age restrictions).   He is not being considered a qualifying child (max age 24).   Since he made less than $4400, he can be your qualifying relative dependent.   He qualifies you for the Other Dependent (Family) Tax Credit of $500.   

You can see the difference in this FAQ.    You can see on Form 1040-Dependents section (4) will have an x in the Credit for other deps. column, not in the Child tax credit (larger credits apply) column.  

[ajartax]

@DawnC 

My son had already filed his return in which he did not mark the checkbox "somebody can claim him as dependent".  After that when I (his parent) tried to e-file our tax return, it was rejected because we were claiming him as dependent.  So my son amended his 2022 tax return and this time he marked the checkbox that somebody can claim him as dependent.  This amended tax return was accepted.  But our (parent) tax return is still getting rejected due to same reason.  It seems, we need to wait for his amended tax return to process before we can efile ours.  If that does not happen until 15th of April, what do we do?  Should we file an extension or just mail a paper tax return? Or is there any other option?

[xmasbaby0]

@ajartax You will have to file by mail this year.   Even if your son amended, the amended return will not catch up in the system this year to allow you to e-file.  Waiting will not help you.   Print, sign and mail your own return that claims your son as a dependent.   

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

[Hal_Al]

Q. It seems, we need to wait for his amended tax return to process before we can efile ours.  If that does not happen until 15th of April, what do we do?  Should we file an extension or just mail a paper tax return? Or is there any other option?

A. His amended return will definitely NOT be processed by April 15. You should just file a paper return, because it will never be clear when his amended return has been fully processed, and  it is safe for you to e-file. 

[ajartax]

Will filing extension be of any help?

Thank you!