My son and daughter are living with me for the last year, if I claim them as dependents does it affect his own tax return?

[userrikersls]

he has already filed as head of household and I don't want to get him in trouble if I file with him as a dependent, he is a full time worker and he helps with house expenses

[HelenC12 · Accepted solution]

Yes, it would affect his taxes negatively since he already filed and claimed Head of Household. He would need to file an amended tax return and return any overpayment he received initially. Also, he probably doesn't qualify as your dependent. 

Here are the requirements to claim a dependent on your 2020 taxes:

Qualifying child

• They're related to you.
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They're under the age of 19 (or 24 for full-time students).
  • No age limit for permanently and totally disabled children.
• They lived with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.

Qualifying relative

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,300 in 2020.
• You provided more than half of their financial support.

When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.