The federal government does not recognize domestic partners as married individuals, therefore, they continue to file unmarried individuals on their federal return. You may use form 8958 to allocate your income for computation only, You have to enter the i/2 of the community property income only as other income on line 8 of 1040 from Schedule 1, line 9 and enter the description " filing RDP joint in California return . On form 8958, allocate income (wages, interests, dividends and many more), self-employment taxes only, and more
See. form 8958, link for instruction
