Can You Require a Cosigner or Guarantor in Washington?

An applicant you like comes in just under your income bar. Their credit is thin rather than bad. Then the offer arrives: "My mom will cosign." It is one of the most common moments in leasing, and Washington handles it in a way that catches owners off guard. The state has almost nothing to say about cosigners directly, yet the one place it does mention them creates a paperwork duty most landlords have never heard of.

Here is what Washington law actually permits, what it requires you to document, and the two mistakes that turn a routine cosigner request into real liability.

The Short Answer: Legal, and Barely Regulated

Search the entire Residential Landlord-Tenant Act for "cosigner" and you will find nothing. The word does not appear in RCW 59.18 at all. Neither does "co-signer," "joint and several," or "co-tenant." Washington sets no guarantor qualifications, no liability limits, and no duration rules. Everything beyond the statute is ordinary contract law.

"Guarantor," though, appears exactly once. And it appears in a place that matters.

The Adverse Action Trap in RCW 59.18.257

Washington's tenant screening statute, RCW 59.18.257, contains a notice form landlords must use when they take adverse action on an application. The form's checkboxes read, in part:

"This notice is to inform you that your application has been: ..... Rejected ..... Approved with conditions: ..... Residency requires an increased deposit ..... Residency requires a qualified guarantor ..... Residency requires last month's rent ..... Residency requires an increased monthly rent of $........"

Read that carefully, because it cuts both ways. The legislature clearly contemplates that you may require a guarantor. That is your permission slip. But it puts the requirement in the adverse action form, alongside rejection. Telling an applicant "you're approved, just get me a cosigner" is legally an adverse action, and it obligates you to serve written notice stating the decision and the reasons for it.

Notice the company that requirement keeps. An increased deposit, last month's rent, and a higher monthly rent sit in the same list. All four are equally permitted and all four equally trigger the notice. If you are already serving adverse action notices properly, adding a guarantor condition costs you nothing procedurally. If you are not, every conditional approval you have issued is exposed.

Disclose It Before You Screen, Not After

RCW 59.18.257(1)(a) is emphatic about sequence:

"Prior to obtaining any information about a prospective tenant, the prospective landlord shall first notify the prospective tenant in writing, or by posting, of the following: (i) What types of information will be accessed to conduct the tenant screening; (ii) What criteria may result in denial of the application ..."

A guarantor requirement is plainly a criterion that can result in denial, so it belongs in your written screening criteria, published before you run the first report. And the statute ties your fee to that disclosure: you may charge for a screening report "only if" you provided the required information first. Skip the disclosure and you have forfeited the fee, with a penalty of up to $100 plus court costs and reasonable attorneys' fees. Our guide to screening tenants legally in Washington walks through the full disclosure packet.

Cosigner or Guarantor? Your Document Decides

These words get used interchangeably, including by the state landlord association, but they describe different deals:

• A cosigner signs the lease as a co-tenant. Jointly liable from day one, and legally entitled to occupy the home.
• A guarantor signs a separate guaranty promising to pay if the tenant defaults. Secondarily liable, with no right of possession.

Washington defines neither term, which means the label on the page decides nothing. The operative language does. If you want someone financially responsible but not entitled to move in, use a separate guaranty and say so explicitly.

Get It in Writing, and Make It Explicit

This is the rule that voids more guaranties than any other. RCW 19.36.010 provides that an agreement "shall be void, unless ... in writing, and signed by the party to be charged," and subsection (2) applies that to "every special promise to answer for the debt, default, or misdoings of another person." A guaranty is exactly that. An oral cosign promise is worth nothing in Washington. If the lease runs longer than a year, subsection (1) independently demands a writing.

Washington courts also read guaranties narrowly and against the landlord who drafted them. In Seattle-First National Bank v. Hawk, 17 Wn. App. 251 (1977), and again in Wilson Court Limited Partnership v. Tony Maroni's, Inc., 134 Wn.2d 692, 952 P.2d 590 (1998), the courts held that a guarantor's promise must be explicit and is strictly construed. A guarantor's obligation does not get extended by implication.

The practical consequence is a drafting instruction. Because ambiguity cuts against you, your guaranty should state expressly that it is a continuing guaranty covering renewals, extensions, a rollover into month-to-month, and rent increases, and that the guarantor waives notice of those modifications. Silence on any of those points is silence you will not enjoy litigating. This matters most at renewal time, when the original tenancy quietly becomes a different one.

The Fair Housing Half, Which Is Where the Money Is

Cosigner requirements are where a neutral-sounding policy turns into a discrimination claim. Three things to get right.

1. Subtract the voucher before you do the math

RCW 59.18.255(3) could not be clearer:

"If a landlord requires that a prospective tenant or current tenant have a certain threshold level of income, any source of income in the form of a rent voucher or subsidy must be subtracted from the total of the monthly rent prior to calculating if the income criteria have been met."

Run a 3x test against $2,000 of full contract rent when the tenant's share is $400, conclude they fall short, and demand a cosigner, and you have violated the statute. The exposure is not trivial: up to four and one half times the monthly rent, plus costs and attorneys' fees. Source of income is defined broadly and covers housing assistance, veterans benefits, social security, and SSI. We cover the whole framework in can you refuse Section 8 in Washington.

2. Apply the rule to everyone or to no one

Washington's protected classes for housing are listed in RCW 49.60.222, and the list is longer than most owners realize: sex, marital status, sexual orientation, race, creed, color, national origin, citizenship or immigration status, families with children status, honorably discharged veteran or military status, disability, and use of a service animal or trained dog guide.

So a habit of asking families with kids for a cosigner, or asking non-citizens for one, is discriminatory on its face. "Students" and "no credit history" are not protected categories by themselves, but a criterion you apply inconsistently is textbook evidence of disparate treatment. Write the rule down, apply it to every applicant identically, and you remove the argument. See fair housing laws every Vancouver landlord must follow.

3. Never adopt a blanket "no cosigners" policy

Here is the counterintuitive one. Owners often ban cosigners outright, reasoning that a tenant who cannot qualify alone should not be housed. The Ninth Circuit, whose rulings bind Washington, rejected that in Giebeler v. M & B Associates, 343 F.3d 1143 (2003). The applicant had AIDS, could not work, lived on disability income, and failed the minimum income test. His mother met the standard and offered to cosign. The landlord's no-cosigner policy refused her. From the opinion:

"The question in this case is whether the Fair Housing Amendments Act ... required the apartment owners reasonably to accommodate Giebeler's disability by assessing individually the risk of nonpayment created by his specific proposed financial arrangement, rather than inflexibly applying a rental policy that forbids cosigners. Concluding that the statute does so require, we reverse ..."

A rigid ban does not protect you. It creates a duty to make exceptions, and a lawsuit when you refuse. Allowing cosigners under a consistent, written standard is the safer posture.

The Alternatives, and One Myth to Retire

A guarantor is not your only lever. The RCW 59.18.257 checklist itself offers three more, all equally permitted and all equally adverse actions: an increased deposit, last month's rent, or a higher monthly rent.

On deposits, retire a myth you will read everywhere: Washington does not cap security deposits on ordinary residential rentals. House Bill 1217 (2025) did create a one-month deposit and move-in fee cap, but it wrote that rule into RCW 59.20.170, which governs manufactured and mobile home communities. Standard tenancies under RCW 59.18 got the rent cap, not the deposit cap. Sources repeating "Washington now limits deposits to one month's rent" are conflating two different statutes.

Real constraints that do apply to your deposit strategy:

• RCW 59.18.253: a hold fee cannot exceed 25 percent of the first month's rent, and it must be credited toward rent or the deposit.
• RCW 59.18.285: nonrefundable fees cannot be called a "deposit," and a written rental agreement is required to charge them.
• RCW 59.18.610: tenants may pay deposits, nonrefundable fees, and last month's rent in installments.
• The voucher trap again: a larger deposit imposed specifically on a voucher holder is source-of-income discrimination under RCW 59.18.255(1)(c).

Our Washington security deposit guide covers the accounting and the 30-day return clock in detail.

Where This Is Heading

Vancouver landlords are on the state baseline today. The city's rental registration program (VMC 5.08) began charging its $30 per unit annual fee on March 31, 2026, but it contains no screening or cosigner provisions.

Elsewhere in Washington, cities are starting to legislate the exact moment this article is about. Olympia's ordinance, effective April 1, 2026, caps income requirements at 2.5 times rent and expressly permits requiring a cosigner when an applicant's income falls below that line. That rule does not apply in Vancouver or Clark County. It is worth watching as a signal of where the state's thinking is going, and as one more reason to keep your written criteria current. Meanwhile, HB 1217's rent cap limits 2026 increases for RCW 59.18 properties to 9.683 percent, which changes the "just raise the rent instead" option you might have reached for.

The Practical Routine

• Publish your criteria first, including when a guarantor is required, before you pull a single report.
• Set the guarantor standard in writing and higher than the tenant standard, then apply it to every applicant the same way.
• Serve the adverse action notice every time you condition an approval on a guarantor. Every time.
• Subtract subsidies before any income calculation, without exception.
• Use a signed, explicit, continuing guaranty that names renewals, rollovers, and rent increases.
• Screen the guarantor with your standard process. Nothing prohibits it, and their finances are the whole point of the arrangement.

Frequently Asked Questions

Can a landlord require a cosigner or guarantor in Washington State?

Yes. No Washington statute prohibits it, and RCW 59.18.257(1)(c) implicitly permits it by listing "Residency requires a qualified guarantor" as one of the conditions a landlord may attach to an approval. The catch is that the same statute treats it as an adverse action, so you must serve the applicant written notice of the decision and the reasons for it.

What is the difference between a cosigner and a guarantor?

A cosigner signs the lease itself as a co-tenant. They are jointly liable for the rent from day one and they have the right to occupy the home. A guarantor signs a separate guaranty and promises to pay if the tenant does not, but has no right to move in. Washington law does not define either term, so the distinction depends entirely on how your documents are written, not on which label you use.

Does a lease guaranty have to be in writing in Washington?

Yes. RCW 19.36.010(2) makes "every special promise to answer for the debt, default, or misdoings of another person" void unless it is in writing and signed by the person being held responsible. An oral promise from a parent to cover their adult child's rent is unenforceable in Washington. If the lease term runs longer than one year, RCW 19.36.010(1) requires a writing as well.

Can I require a cosigner from a Section 8 voucher holder?

Be very careful. RCW 59.18.255(3) requires that any rent voucher or subsidy be subtracted from the monthly rent before you apply an income threshold. If you apply a three-times-rent test to the full contract rent, decide the voucher holder fails, and demand a cosigner on that basis, you have violated the statute. Damages run up to four and one-half times the monthly rent, plus costs and attorneys' fees.

Is a no-cosigner policy safer for landlords?

No, and this surprises most owners. In Giebeler v. M & B Associates, 343 F.3d 1143 (9th Cir. 2003), a policy that flatly forbade cosigners was held to violate the Fair Housing Amendments Act when applied to a disabled applicant whose mother met the income standard and offered to cosign. The Ninth Circuit, which covers Washington, held that waiving the no-cosigner rule was a required reasonable accommodation. A blanket ban creates liability rather than avoiding it.

Does Washington cap security deposits at one month's rent?

Not for standard residential rentals. This is a widely repeated error. House Bill 1217 (2025) did add a deposit and move-in fee cap of one month's rent, but it wrote that cap into RCW 59.20.170, which governs manufactured and mobile home communities. Ordinary residential tenancies under RCW 59.18 have no general statutory deposit cap. Other limits still apply, including the 25 percent hold fee limit in RCW 59.18.253 and the installment rules in RCW 59.18.610.

This article is general information for Washington rental owners, not legal advice. Guaranties are contract law and screening decisions carry fair housing exposure, including damages of up to 4.5 times the monthly rent under RCW 59.18.255. Confirm current requirements with the statute or a qualified Washington attorney before acting.

Written by Avenir Gedarevich, Washington State Designated Broker (License #25011405) at VPMG Property Management in Vancouver, WA.