It depends. Simply having your domestic partner on your insurance doesn't mean you can claim him/her as a dependent on your income taxes.
A domestic partner can be claimed as a dependent if they pass some of the same tests used to determine if your child or relative can be claimed as a dependent.
You can claim your partner as a dependent if your situation meets all of the following conditions:
- No one else, such as your partner's parents, can claim your partner as a dependent child on their tax return
- Your partner must be a U.S. citizen, a U.S. national, a U.S. resident alien, or a resident of Canada or Mexico
- Your partner must live with you all year
- Your partner's gross income for the year—meaning income from all sources—cannot exceed the exemption amount. For 2017, that amount is $4,050
- You must provide more than half of your partner's financial support during the year
- Your partner cannot be married to someone else and file a joint return with that other person except to claim a refund of withheld income tax or estimated income tax paid
