The tax basics of subletting a room in California
Money received for use or occupancy of a room is generally rental income for federal and California tax purposes. The treatment of expenses can depend on personal use, the length of the rental, services provided, and other facts. A security deposit intended to be returned is treated differently from rent kept or used as the final payment.
Keep the sublease, rent ledger, deposit record, utility bills, platform statements, and receipts for ordinary rental-related expenses. Do not assume that charging only enough to cover your own rent makes the income irrelevant for taxes.
Use current IRS and California Franchise Tax Board guidance, then consult a tax professional for your return.
Sources: IRS rental-income guidance, California FTB rental income.