If they wish to claim him and he meets the qualifications for them to do so, you can't file jointly with him. There are two possible ways to qualify but see the last point in bold.
Qualifying child
In addition to the qualifications above, to claim an exemption for your child, you must be able to answer "yes" to all of the following questions.
- Are they related to you? The child can be your son, daughter, stepchild, eligible foster child, brother, sister, half-brother, half-sister, stepbrother, stepsister, adopted child or an offspring of any of them.
- Do they meet the age requirement? Your child must be under age 19 or, if a full-time student, under age 24. There is no age limit if your child is permanently and totally disabled.
- Do they live with you? Your child must live with you for more than half the year, but several exceptions apply.
- Do you financially support them? Your child may have a job, but that job cannot provide more than half of her support.
- Are you the only person claiming them? This requirement commonly applies to children of divorced parents. Here you must use the “tie-breaker rules,” which are found in IRS Publication 501. These rules establish income, parentage, and residency requirements for claiming a child.
Qualifying relative
Here is a checklist for determining whether a relative qualifies.
- Do they live with you? Your relative must live at your residence all year or be on the list of “relatives who do not live with you” in Publication 501. About 30 types of relatives are on this list.
- Do they make less than $4,300 in 2020 or 2021? Your relative cannot have a gross income of more than $4,300 in 2020 or 2021 and be claimed by you as a dependent.
- Do you financially support them? You must provide more than half of your relative’s total support each year.
- Are you the only person claiming them? This means you can’t claim the same person twice, once as a qualifying relative and again as a qualifying child. It also means you can’t claim a relative—say a cousin—if someone else, such as his parents, also claims him.
For both types of dependents, you’ll need to answer the following questions to determine if you can claim them.
- Are they a citizen or resident? The person must be a U.S. citizen, a U.S. national, U.S. resident, or a resident of Canada or Mexico. Many people wonder if they can claim a foreign-exchange student who temporarily lives with them. The answer is maybe, but only if they meet this requirement.
- Are you the only person claiming them as a dependent? You can’t claim someone who takes a personal exemption for himself or claims another dependent on his own tax form.
- Are they filing a joint return? You cannot claim someone who is married and files a joint tax return. Say you support your married teenage son: If he files a joint return with his spouse, you can’t claim him as a dependent.
