If claim my Son as a dependent can I also claim my daughter in law and grandchild?

[rhansen]

My son is married and has a son; he earned very little in 2020, I paid for almost all of his and his families expenses.  He submitted a joint return and claimed his wife and son as dependents,  Since he made less than $4,300 I know that I can claim a Tax Credit for him as an Other Dependent but can I also claim his wife and son as Other Dependents?  

[ColeenD3]

Yes, but only if your son amends and says that he is being claimed and removes his child from his own return. Please see the asterisk below. I am assuming the wife also made no money. Your grandchild could be a Qualifying Child if he lived with you. You would have to mail in your return.

Qualifying Child

Relationship — the taxpayer’s child or stepchild (whether by blood or adoption), foster child, sibling or step-sibling, or a descendant of one of these.

Residence — has the same principal residence as the taxpayer for more than half the tax year. Exceptions apply, in certain cases, for children of divorced or separated parents, kidnapped children, temporary absences, and for children who were born or died during the year.

Age — must be under the age of 19 at the end of the tax year, or under the age of 24 if a full-time student for at least five months of the year, or be permanently and totally disabled at any time during the year.

Support — did not provide more than one-half of his/her own support for the year.

*Marital status — if married, did not file a joint return for that year, unless the return is filed only as a claim for refund and no tax liability would exist for either spouse if they had filed separate returns.

[NCperson]

because of the complexity, you might run your scenario through the IRS dependent tool: 

https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent

[Opus 17 · Accepted solution]

Starting from zero and assuming no tax return had been filed:

1. You can claim your son as a dependent if he earned less than $4300 AND you provided more than half his support.  This is a $500 credit to you, but no stimulus rebate. 
2. You can claim your grandson as a "qualifying relative dependent" if his income is less than $4300 and you provided more than half his support.  This is a $500 credit to you.  To claim him as a "qualifying child dependent", he would have to live in your home more than half the year. This would be a $2000 credit, plus possibly a stimulus rebate of $1000.  
3. You can claim your daughter in law as a dependent only if she had less than $4300 of taxable income, AND you provided more than half her support, AND she lived in your home the entire year.  This would be a $500 credit and no rebate. 

Now, the fact that your son already filed a joint return bars you from claiming him or his wife as dependents, and the fact that he claimed your grandson bars you from claiming your grandson.  Before you could claim your son as a dependent, he would have to file an amended tax return to change from "married filing jointly" to "married filing separately" and to remove his son (because someone who is a dependent can't claim a dependent), and the deadline to do this is May 17, 2021.  Then, his wife would also file as "married filing separately" if she had income to report.

No one can tell how this would work out without testing your exact circumstances, but for 2020, the odds are that they get much more money filing the way they did.  As is, even with no income, they are eligible for $2900 in round 1 stimulus and $2300 in round 2 stimulus (or rebate, if they did not get stimulus checks) and $4200 in round 3 stimulus payments, plus possibly some earned income credit.   You would not get any round 1 or round 2 rebate by claiming the adults, because dependents over age 16 are excluded.  You would get the $1400 round 3 payment for each dependent you claimed, but they would not get the payments.  Plus, if you change things now, and there are extra or duplicate payments made because different tax returns are crossing in the system, the extra or duplicate payments would have to be repaid.