When several roommates sign one California lease and all share the home, each is presumed to be liable for the whole lease obligation, not just a share: Civil Code § 1659 presumes a promise is "joint and several" when everyone who joins in it benefits from it. That is a presumption, because the general rule in § 1431 runs the other way, so the lease should say "jointly and severally" in plain words. The security deposit follows the tenancy, not the person: it is accounted for within 21 days after the tenant vacates under § 1950.5, not each time one roommate moves out.

The short version

  • Two Civil Code sections presume co-tenants are jointly and severally liable: § 1659 (everyone who joins the promise benefits) and § 1660 (a promise in the singular, such as "Tenant agrees," signed by several people).
  • The default rule in § 1431 is the opposite, "joint, and not several," except in those special cases. A lease that says "jointly and severally" removes the doubt.
  • The deposit refund is tied to the end of the tenancy. Without a written agreement with all adult tenants, it goes back as one check payable to all of them (§ 1950.5(h)(1)(C)).
  • Adding an adult roommate can change when just-cause protection applies (§ 1946.2(a)).
  • State law has no rule requiring a landlord to accept a replacement roommate. The lease controls, subject to any local ordinance.
  • Income standards must count roommates' combined income the same way they would count a married couple's (Gov. Code § 12955(n)).

How joint and several liability works

Section 1431 says an obligation imposed on several persons "is presumed to be joint, and not several," except in "the special cases mentioned in the title on the interpretation of contracts." Two of those special cases fit a shared lease:

  • Section 1659: "Where all the parties who unite in a promise receive some benefit from the consideration, whether past or present, their promise is presumed to be joint and several." Roommates who all sign and all live in the home fit that description.
  • Section 1660: "A promise, made in the singular number, but executed by several persons, is presumed to be joint and several." A lease that says "Tenant shall pay" and is signed by three people falls here.

Joint and several means each signer can be held responsible for the full obligation, not only a share of it. Because these are presumptions, the cleanest approach is to state the rule in the lease so nobody has to argue about it later. Any agreement roommates make about splitting rent is between the roommates; keep it separate from the lease.

What the clause should cover

ItemWhat to includeWhy
Who signsEvery adult who will live in the home as a tenantNo statute covered here requires every adult to sign, but signers are the people bound by the lease
Liability statementThat all tenants are jointly and severally liable for rent and every other lease obligationTurns the § 1659 and § 1660 presumptions into an express term
Named occupantsEveryone who may live there, including minorsTies into occupancy and guest clauses
Rent paymentWhether rent comes as one payment or several, and the accepted methodsCivil Code § 1947.3 requires at least one method that is neither cash nor electronic transfer
Roommate leavingThe written notice a departing roommate gives and whether a release needs the owner's signatureThe statutes covered here do not say whether one co-tenant's notice ends the tenancy for all
Replacement roommateHow a replacement applies, who screens, and how the new person is addedState law sets no replacement rule; the lease fills the gap
Deposit refundWhether the tenants agree in writing to split the refund by percentage or methodOtherwise § 1950.5(h)(1)(C) requires one check payable to all adult tenants

When a roommate wants to leave

  1. Read the lease. If it is a month-to-month tenancy, Civil Code § 1946(a) lets a tenant end it with at least 30 days' written notice. The statutes covered here do not say what happens when only one of several co-tenants gives notice, so do not assume the notice ends or does not end the tenancy for everyone. Put your approach in the lease and ask an attorney before acting on a partial notice. See termination notices.
  2. Decide who stays. The remaining roommates and the owner should agree in writing whether the tenancy continues with them, and whether the departing roommate is released from future obligations.
  3. Settle the deposit share. The refund under § 1950.5 is due no later than 21 calendar days after the tenant has vacated. When one roommate leaves and the tenancy continues, the deposit generally stays in place until the tenancy ends, and the outgoing and incoming roommates settle that share between themselves. See security deposits.
  4. Walk the space. Dated photos of the departing roommate's room and the shared areas help everyone later, even though no statute requires them at that point.
  5. Screen the replacement under the same written criteria you use for any applicant, then sign an addendum adding them. The subletting and assignment clause page covers the consent process.

A tenant who ends a lease because of domestic violence or certain other crimes follows separate rules in Civil Code § 1946.7, including rules about co-tenants. See domestic violence lease termination.

Adding a roommate and the just-cause clock

Just-cause protection under Civil Code § 1946.2 starts after a tenant has continuously and lawfully occupied the home for 12 months. If adult tenants are added before an existing tenant reaches 24 months, the protection applies only once all tenants have 12 months, or at least one has 24 months (§ 1946.2(a)). Adding a roommate in year one can therefore push back the date protection begins. Owners should not use that rule to pressure anyone, and renters should understand it before adding someone. See just-cause eviction.

Screening a new roommate follows the usual rules:

  • A screening fee is limited by Civil Code § 1950.6, and "applicant" includes guarantors and cosigners.
  • An income standard must account for the aggregate income of people living together on the same basis as a married couple's (Gov. Code § 12955(n)). Under 2 CCR § 12142, a provider that combines married persons' income must do the same for unmarried cohabitants.
  • Decisions may never turn on a protected characteristic, including familial status, source of income, disability, or military or veteran status (Gov. Code § 12955).

The deposit when roommates change

Under § 1950.5(h)(1)(C), unless there is a written agreement with all adult tenants, the landlord refunds the deposit with one check payable to all adult tenants. A written agreement may set allocation percentages and methods, including electronic deposit to each tenant. Since January 1, 2026, if the deposit or rent was paid electronically, the balance must go back electronically to an account the tenant designates in writing, unless the parties agree in writing on another method (§ 1950.5(h)(1)(A)). Agreeing on the split at signing saves an argument at move-out.

Clause mistakes to avoid

  • Relying on the presumption instead of writing "jointly and severally liable" into the lease.
  • Promising a departing roommate a partial refund of the deposit before the tenancy ends, with no written agreement from the others.
  • Assuming one roommate's notice ends, or does not end, the tenancy for everyone.
  • Letting a replacement move in without an application, screening or a signed addendum.
  • Applying income rules that count roommates' income differently from a married couple's.

For owners

Have every adult tenant sign, write the joint and several statement into the lease, and agree in writing how the deposit refund will be split. Handle roommate changes with a written addendum every time. The first-year landlord checklist is a useful companion for Coronado owners.

For renters

Before you sign with roommates, understand that you may be held to the full rent if someone else does not pay. Keep a written roommate agreement on shares and chores, ask the owner in writing before anyone moves in or out, and agree with your roommates and the owner on how the deposit refund will be split.

Local rules

Some cities add rules on top of state law, such as local just-cause, relocation or rental registration rules, and some local rent ordinances include replacement-roommate rules; check your city's code. Coronado has no local rent-control or just-cause ordinance as of October 2026 (based on a review of its code's contents).

Frequently asked questions

Is each roommate responsible for all of the rent in California?

Usually, by presumption. Civil Code § 1659 presumes a promise is joint and several when everyone who joins it benefits from it, and § 1660 does the same for a promise in the singular signed by several people. The general rule in § 1431 is the opposite, so a lease that states "jointly and severally liable" is the clearest way to settle it.

Does a roommate who moves out get their share of the deposit back?

Not automatically from the landlord. Section 1950.5 ties the refund to 21 calendar days after the tenant has vacated, and without a written agreement with all adult tenants the refund is one check payable to all of them. When the tenancy continues, outgoing and incoming roommates usually settle the share between themselves.

Can one roommate end the lease for everyone?

The statutes covered here do not answer that. For a month-to-month tenancy, Civil Code § 1946(a) lets a tenant give at least 30 days' written notice, but whether one co-tenant's notice ends the tenancy for all is not settled by those sections. Put a rule in the lease and ask a California attorney before acting on it.

Does adding a roommate affect just-cause protection?

It can. If adult tenants are added before an existing tenant reaches 24 months, Civil Code § 1946.2(a) applies just-cause protection only once all tenants have 12 months of occupancy or at least one tenant has 24 months.

Must a landlord accept a replacement roommate?

California state law sets no such rule; Civil Code § 1946.2 contains none. The lease's clause controls, and some local ordinances have replacement-roommate rules, so check your city's code.

McKee Properties manages rentals from its Coronado office; contact us with questions about your property.

This is general information, not legal advice. Laws change; confirm the current text and your situation with a California attorney.

Sources

Verified October 19, 2026.

Talk With a Local Property Expert

Ask your questions, get honest answers, and see if we’re the right fit — no commitment.

Schedule a Call