It depends. First, decide who meets the rules to claim the child. See: Who can I claim as a dependent?
Second, check if the child appears on the mom's return on page 1 of Form 1040. If yes, then the father cannot claim the child unless the mom files an amended return.
If no, then if the father is not the custodial parent, he will need the mother to provide him with Form 8332 if the parents are no longer married. See 2019 Form 8332 and Instructions.
Click the links for more details:
- Tricky Dependent Situations
- Qualifying Relative Tests
- IRS Whom may I claim as a dependent? interactive tax assistant
Are you two unmarried parents living together or divorced or separated parents?
If you and the other parent live together, only one of you can claim the child for any tax benefit. The interview is confusing (it's designed for divorced parents, who are allowed to split the child). The second parent should not enter the child, at all.
If you and the other parent live together, either one of you (but not both) may claim the child. You may decide between you which one will claim the child. Only if you can’t agree, do the IRS tie breaker rules apply, to see who has first choice. It may be worthwhile to prepare trial returns, both ways, to see which way the family comes out best. This tool may be useful: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1.
There is a special rule in the case of divorced & separated (including never married) parents. When the non-custodial parent is claiming the child as a dependent/exemption/child tax credit; the custodial parent is still allowed to claim the same child for Earned Income Credit, Head of Household filing status, and day care credit. This "splitting of the child" is not available to parents who lived together at any time during the last 6 months of the year; then only one of you can claim the child for any tax reasons. The tax benefits may not be split in any other manner.
Note in particular that the non-custodial parent can never claim the Earned Income Credit, Head of Household filing status or the day care credit, based on that child, even when the custodial parent has released the dependency to him.
So, it's good idea to let the other parent know that you will be claiming those items, as many first time divorced parents are not aware of this rule and may try to claim those items, which will cause the IRS to send out letters.
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