There is no way to know who else might have claimed your dependent as a dependent on their tax return. If he qualifies to be your dependent and he filed his own return, he should have indicated on his return that he can be claimed by someone else. Ask your dependent if he indicated on his return that he can be claimed by someone else. If he did not indicate that but should have, then he will have to prepare and mail an amended return form 1040X to indicate that on his return. You would have to print and mail your return to get it accepted.
You would also have to print and mail your return to get it accepted if your dependent's father claimed him and shouldn't have claimed him. The IRS will then sort out later in the year who could rightfully claim him as a dependent.
If the dependent you claimed does not qualify to be claimed as your dependent, then you need to delete him as indicated in the answer from TurboTaxVanessa.
Thank you, cool. I just deleted him on my taxes, as he's now filing his own I figure I'll just have to deal with that loss of $500 deduction - at least I am doing it right, where his father is usually not, haha! Thank you!
Perhaps I wasn't clear about whether or not he can claim himself. If he meets the requirements to be claimed by you, he cannot claim himself on his tax return. Many dependents file their own tax return but can and are still claimed by a parent as a dependent. There are two types of dependents--qualifying child and qualifying relative. Here are the requirements for each:
Qualifying Child Requirements
1. The child must be your son, daughter, stepchild, foster chld, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student, or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you (or your spouse, if filing jointly) unless disabled.
If he does not qualify to be a qualifying child dependent, he might qualify to be a qualifying relative.
Qualifying Relative Requirements
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross taxable income for the year must be less than $4,150 in 2018.
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico.