See this TurboTax support FAQ for information on domestic partnerships - https://ttlc.intuit.com/community/married/help/how-do-i-prepare-my-return-if-i-m-in-a-registered-dom...
If your partner did not have gross income in 2021 of $4,300 or more you may be able to claim them as a dependent on your tax return under the Qualifying Relative rules. If not legally married, you will have to file as Single if you do not have a qualifying person as a dependent. An unrelated partner is not a qualifying person for Head of Household filing status.
To be a Qualifying Relative -
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 income for the year must be less than $4,300 (social security does not count) in 2021
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 or a U.S., Canada, or Mexico resident for some part of the year.
6. The person must not file a joint return with their spouse.
