Can a California landlord raise rent during a fixed-term lease?

Generally no. A fixed-term lease in California locks the rent amount for the lease term. A landlord cannot raise rent during a fixed-term lease without the tenant's written agreement, regardless of whether the market rent has changed. On a month-to-month tenancy or after the fixed term expires, the landlord may increase rent with the required advance notice. California requires 30 days notice for rent increases of 10% or less and 90 days notice for increases above 10%. AB 1482 caps annual increases at the lower of 5% + local CPI or 10% flat, with exemptions for natural-person single-family owners and buildings under 15 years old.

Source: Cal. Civ. Code 827(b)