California defines a single member LLC as a Disregarded Entity because the single owner's income is treated as a Sole Proprietor on the Federal Schedule C (per the IRS instructions). While a single member LLC does not file California Form 565, they must file California Form 568 which provides details about the LLC.
Per the CA website Limited Liability Company (LLC):
All LLCs classified as partnerships or disregarded entities that organize in California, register in California, or conduct business in California, must file California Form 568 Limited Liability Company Return of Income. California Form 568 must be filed by the 15th day of the 3rd month after the close of the LLC’s taxable year.
To enter the information for Form 568 in the 1040 TaxAct® program:
Note. Schedule IW, Limited Liability Income Worksheet, is included at the bottom of the Form 568 which is used to populate the figure on Form 568, Line 1.
Note. TaxAct supports e-file for one copy of Form 568 in the 1040 product. Additional copies will need to be paper-filed.