What if a California rent increase violates the cap?
An increase above Cal. Civ. Code 1947.12's cap is unenforceable. The tenant may continue paying the prior rent or the rent at the cap level. The excess is not legally owed. The tenant may also seek refund of any excess paid plus, in some states, attorney fees and damages. 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. Reporting to the state housing agency (where applicable) is an additional remedy. Most California small landlords settle quickly when the cap is pointed out.
Source: Cal. Civ. Code 827(b)
This is an informational answer based on Cal. Civ. Code 827(b) as of early 2026. It is not legal advice. Housing law changes year to year and local ordinances (especially in rent-controlled or rent-stabilized cities) can override or add to state law. For contested cases, consult a California-licensed attorney.