No, registered domestic partners may not file federal tax returns using a married filing jointly or married filing separately status.
For federal tax purposes, registered domestic partners are not considered married. Therefore, they must use the single filing status or, if they qualify, the head of household filing status. This is consistent with the IRS's position that registered domestic partners, civil unions, or other similar formal relationships that are not denominated as a marriage under state law are not recognized as marriages for federal tax purposes. Consequently, the terms "spouse," "husband and wife," "husband," and "wife" do not include individuals in such relationships, and the term "marriage" does not include these relationships.
Registered domestic partners must report their income and deductions separately, and they are required to use Form 8958, Allocation of Tax Amounts Between Certain Individuals in Community Property States, to determine the allocation of tax amounts between them. Each partner must complete and attach Form 8958 to their individual Form 1040.
Sources:
Rev. Rul. 2013-17
Publication 555 (3/2020)
§ 7703. Determination of marital status
IRS FAQ
IRM Part 25. Special Topics. Chapter 18. Community Property. Section 1. Basic Principles of Community Property Law
IRM Part 21. Customer Account Services. Chapter 6. Individual Tax Returns. Section 1. Filing Status and Exemption/Dependent Adjustments
