Raising rent is one of the more routine jobs for a housing provider (landlord), and one of the easier ones to get wrong by a small margin. The rules are short once you see them in order, and they answer three questions: how much, how much notice, and does this home follow the state rules at all. If you are planning a January increase, the order below is the order to check them in.
How much can the rent go up?
For most homes, Civil Code 1947.12 (the Tenant Protection Act, from Assembly Bill 1482) sets the ceiling. Over any 12-month period, rent may not go up by more than 5 percent plus the change in the cost of living, or 10 percent, whichever is lower. The starting point is the lowest rent charged for that home at any time in the 12 months before the new rent starts.
Two details matter in the math. Discounts and credits the owner offered and the resident accepted are left out when finding that lowest rent, and the lease has to list the gross monthly rent and any discounts separately. And a new tenancy, where no resident from the prior one is still living there, can start at whatever rent the owner sets; the ceiling applies to the increases after that.
The cost-of-living part comes from the Consumer Price Index for the San Francisco-Oakland-Hayward area, which the statute assigns to Contra Costa County. For an increase that starts before August 1, it compares April of the last two years. From August 1 on, it compares the latest April with the April before it. That is why the number resets every August. You do not have to calculate it yourself: the Attorney General publishes a chart (informational only, the statute governs).
| Increase starts | Ceiling for Contra Costa County |
|---|---|
| August 1, 2025 through July 31, 2026 | 6.3 percent |
| August 1, 2026 through July 31, 2027 | 8.8 percent |
Here is how it reads on a real number. A home renting for $2,800 could go up by as much as $246.40 a month at 8.8 percent, to $3,046.40. A 5 percent increase on the same home is $140, to $2,940. Most owners choose well under the ceiling, and a smaller, steady increase is often easier on a good resident relationship than a large one.
Two increases in one year
If the same resident stays, the rent can go up in no more than two steps over any 12 months, and the steps together still have to fit under the ceiling. The same arithmetic decides the notice period, which is the next section.
How much notice, and how to deliver it
Civil Code 827 sets the notice for a month-to-month tenancy. It has to be in writing, and it can be handed to the resident or mailed. Mailing adds days under the Code of Civil Procedure, so build in a few extra.
| The increase, together with any others in the past 12 months | Written notice before it starts |
|---|---|
| 10 percent or less of the rent charged in that period | At least 30 days |
| More than 10 percent | At least 90 days |
| Caused by a required income or household recertification | At least 30 days |
Two more points. If another law or a contract, such as a recorded regulatory agreement, calls for a longer notice, the longer one controls. And Civil Code 827 speaks to month-to-month tenancies. For a fixed-term lease, the rent is whatever the lease says, so the moment to change it is at renewal, which our guide to lease renewals and month-to-month notices walks through.
Timing a January increase
Count forward from the day the notice is delivered. A 30-day notice handed over on December 1 can take effect on January 1. A notice that has to give 90 days needs to be in the resident's hands by early October for a January 1 start. If that date has passed, the next clean start date is simply 90 days from whenever the notice is delivered, plus mailing days if it goes by mail.
Does your home follow the state limit?
Section 1947.12 lists homes it does not cover. The ones most rental owners ask about:
- Newer buildings: housing with a certificate of occupancy issued within the previous 15 years.
- Many single-family homes and condominiums: a home that can be sold separately from any other unit is exempt when the owner is not a real estate investment trust, a corporation, or a limited liability company with a corporation as a member, and the resident was given the exemption notice in writing. For tenancies that started or renewed on or after July 1, 2020, that notice has to be in the rental agreement.
- An owner-occupied duplex: two units in one building where the owner lives in one of them as their main home.
- Housing under a stricter local rent rule, income-restricted housing and school dormitories.
Being exempt from the ceiling does not remove the notice rule. The 30 or 90 day notice in Civil Code 827 still applies to month-to-month tenancies in a residential dwelling.
Antioch and Concord have their own limits
Antioch's Rent Stabilization Ordinance (Municipal Code Title 11, Chapter 3) allows one increase in any 12 months, and the increase cannot be more than the lesser of 3 percent or 60 percent of the most recent 12-month change in the Consumer Price Index for the San Francisco-Oakland-Hayward area. The 12 months run from the last increase. The chapter also sets notice, registration and fee requirements for increases, and the city's Rent Program page shows how those steps work today. The notice itself has to say that the tenancy is regulated by Title 11, Chapter 3, and explain the resident's right to complain or petition. Homes with a certificate of occupancy after February 1, 1995, and single-family homes and condominiums that can be sold separately, are exempt. Check the city's Rent Program page for the current percentage before you set an increase.
Concord (Municipal Code Chapter 19.40, Residential Tenant Protection Program) allows one increase in any 12 months, up to 5 percent since April 1, 2025. No increase is allowed unless the unit is registered and the program's fees are current. The increase has to be made within the program year, August 1 to July 31, or the unused part is waived for the rest of that tenancy. A home that falls under this program follows it instead of the state's Assembly Bill 1482 cap and just-cause rules.
If an increase turns out to be too high
The law spells out what follows. An owner who demands or keeps rent above the ceiling can be required to refund the extra, pay the resident's reasonable attorney fees and costs, and, if the owner acted willfully or with fraud, pay up to three times the extra amount. The Attorney General, a city attorney or county counsel can enforce it, a claim can be brought up to three years later, and a resident cannot sign away these rights in a lease.
If you find a mistake in your own notice, the calm fix is to correct it in writing, restart the notice period with the right number, and refund any difference. Fixing it early costs a conversation. Fixing it late costs more.
Before you send a notice: a short checklist
- Find the lowest gross rent charged for the home in the past 12 months.
- Look up the ceiling for the month the new rent starts.
- Check the exemptions above, and the city's rules if the home is in Antioch or Concord.
- Add up any other increases in the past 12 months, then pick the 30 or 90 day notice.
- Deliver it in writing, by hand or by mail, and keep proof of how and when.
If you are a resident who received an increase notice
Look at three things: the date the new rent starts, how many days of notice you got, and the new rent compared with your rent over the past 12 months. If the numbers look higher than the ceiling, it is reasonable to ask the housing provider (landlord) to show the math in writing; most differences turn out to be a date or a discount that was counted differently. The Attorney General's rent cap page points to LawHelpCA for free legal help if you need it.
Our read, from the operator's chair
A mailed rent-increase notice came back to our office twice. Once that happens, the 30-day count is no longer reliable, so our team looked at hand delivery with a written record instead of mailing it again. Whatever way you deliver the notice, keep proof of how and when it reached the resident.
Where to go from here
Rent increases usually travel with lease renewals, and the notice rules for ending a month-to-month tenancy are a different set from the ones above. The lease renewal guide covers that side. And if you would rather have someone run the math, the notices and the paperwork for your home, a consultation is the simple way to ask how we would do it.
This guide is general information for California rental owners and residents, not legal advice, and laws and local ordinances change. For a specific situation, consult a California landlord-tenant attorney. Croskey Real Estate is an Equal Housing Opportunity provider. DRE #01990430.
Frequently asked questions
How much can a landlord raise rent in California in 2026?
For most homes, the lower of 5 percent plus the local change in the cost of living, or 10 percent, over any 12 months (Civil Code 1947.12). The Attorney General's chart shows 8.8 percent for Contra Costa County for increases that start between August 1, 2026 and July 31, 2027. Exempt homes and some cities follow different limits.
How much notice does a landlord have to give for a rent increase?
At least 30 days in writing if the increase, together with any others in the past 12 months, is 10 percent or less, and at least 90 days if it is more than 10 percent (Civil Code 827). Mailing a notice adds days.
How many times a year can rent go up?
For a covered home with the same resident, no more than two increases in 12 months, and the total still has to stay under the state limit (Civil Code 1947.12).
Does the state rent limit apply to single-family homes?
Often not. A single-family home or condominium that can be sold separately is exempt when the owner is not a real estate investment trust, a corporation or a limited liability company with a corporate member, and the resident received the required written exemption notice. Check the lease for it.
Do Antioch and Concord have different rent rules?
Yes. The Attorney General's chart lists Antioch (60 percent of the change in the Consumer Price Index, up to 3 percent, recalculated every one to two months) and Concord (up to 5 percent) with their own caps. They generally do not reach newer buildings or most single-family homes and condominiums, and the state notice rules still apply.
What happens if a landlord raises rent above the limit?
The owner can be required to refund the extra rent, pay reasonable attorney fees and costs, and, if the owner acted willfully or with fraud, pay up to three times the extra amount. A resident cannot waive these rights in a lease.
