Can a California landlord raise rent more than once a year?

It depends on the tenancy type and any applicable rent control. On a month-to-month tenancy, a California landlord can technically issue multiple rent increases in one year, each with the proper 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.). However, in jurisdictions with rent caps (California's AB 1482, Washington's HB 1217, New York's Good Cause coverage), the annual cap applies regardless of how many increase notices are issued. So even if a landlord delivers two increase notices in 12 months, the combined increase cannot exceed the statutory annual cap. On a fixed-term lease, no increase is permitted during the term unless the lease itself authorizes it, regardless of state. After the term ends, the landlord can issue an increase as part of the renewal offer.

Source: Cal. Civ. Code 827(b)