California's statewide Tenant Protection Act generally caps covered rent increases over a 12-month period at 5% plus the applicable cost-of-living change or 10%, whichever is lower. That formula is not one statewide percentage for every address: regional inflation periods matter, local rent-control laws may be stricter, and exempt properties can follow different rules. Written advance notice is also required.
Information checked: September 10, 2026.
Statewide formula
For most covered older rental housing, Civil Code section 1947.12 limits total increases to 5% plus the percentage change in cost of living, capped at 10%. The correct CPI calculation depends on location and effective date. Use the California Attorney General's current rent-cap page or local agency table.
Common exemptions
Newer housing generally remains exempt for 15 years. Certain owner-occupied duplexes and qualifying separately alienable single-family homes or condominiums can be exempt if statutory ownership and notice conditions are met. Subsidized housing may follow program-specific rules.
Local protections
Cities including Los Angeles, San Francisco, Oakland, Berkeley and others have local rent stabilization rules that may cover different buildings and allow a lower annual adjustment. Local emergency orders or anti-price-gouging rules can add protection after a declared emergency.
Notice periods
California DOJ guidance states that an increase of 10% or less generally requires at least 30 days' written notice, while an increase above 10% requires 90 days. Delivery method affects timing. A call, text or casual email is not a substitute for the formal notice required by law.
How to challenge a notice
Keep the lease, every prior increase and the new notice. Check ownership and construction information, exemption language and local registration records. Write a dated request for the calculation. For eviction threats or complex exemptions, contact a local tenant agency or California lawyer promptly.
Action checklist
Start at the official agency page linked below and confirm that it applies to your location, tax year, account, property, or claim. Write down the deadline and the event that starts it. Gather notices, contracts, statements, payment records, identification, and dated correspondence before submitting. Save a complete copy, confirmation number, delivery proof, and the name of any agency representative. Review the resulting decision promptly and calendar every appeal or follow-up date.
Common mistakes to avoid
Do not rely on an undated search snippet, a commercial calculator, or a rule from another state or county. Do not assume an application pauses a lawsuit, collection action, tax deadline, or housing deadline unless the responsible authority confirms it. Avoid sending original records or sensitive information through an unverified link. When a deadline or legal consequence is disputed, obtain the written rule and consider qualified local advice.
Frequently asked questions
Is the 2026 cap always 10%?
No. It is generally the lower of 5% plus the applicable cost-of-living change or 10%, and local rules may be lower.
Are new buildings covered?
Housing is generally exempt for its first 15 years, subject to the statute.
Does a 90-day notice allow any increase?
No. Notice timing and the lawful amount are separate requirements.
Summary
Check whether the unit is covered, calculate all increases in the prior 12 months, identify the applicable regional CPI period, and compare the result with any city or county cap. A 30- or 90-day notice rule does not make an otherwise excessive increase lawful. Verify current agency instructions before acting.