Cosigner on a Mortgage: Who Can Sign, What It Changes, and the Rules for New Homes
In this article
A cosigner on a mortgage is someone who signs the loan note and shares legal responsibility for the debt, but does not own the home or live in it. Fannie Mae and FHA both allow cosigners and non-occupant co-borrowers, but they set firm limits: the person cannot be the builder, the seller or the real estate agent, and the loan-to-value ratio can be capped lower than on a normal loan.
If a parent, sibling or friend has offered to help you qualify, here is what both sides are signing up for, and what changes when the home is new construction.
What is a cosigner on a mortgage?
Lenders use a few different words for people who help a buyer qualify. Fannie Mae's Selling Guide (section B2-2-04) sets out two groups:
Guarantors and co-signers sign the mortgage note and have joint liability for it with the buyer, but they do not have an ownership interest in the home shown on the title.
Non-occupant borrowers also sign the note and share liability, do not live in the home, and may or may not be on the title.
FHA uses similar language. HUD Handbook 4000.1 (last revised Aug. 12, 2026) says co-signers are liable for the debt and must sign the note, but they do not hold an ownership interest and do not sign the security instrument. FHA's non-occupying co-borrowers, by contrast, must take title to the home and sign all security instruments.
In plain words: a cosigner is on the hook for the loan but has no ownership. A co-borrower is on the hook and usually owns part of the home too.
Who can cosign a mortgage, and who can't?
Most buyers ask a parent or close relative. The bigger rule is about who cannot help.
Fannie Mae says guarantors, co-signers and non-occupant borrowers must not ""have an interest in the property sales transaction, such as the property seller, the builder, or the real estate agent.""
FHA has the same idea. HUD Handbook 4000.1 says a party with a financial interest in the transaction, ""such as the seller, builder or real estate agent, may not be a co-Borrower or a Co-signer."" FHA does allow exceptions when that party is a family member.
FHA adds one more rule: non-occupying co-borrowers and co-signers must be U.S. citizens or have their principal residence in the United States.
How does a cosigner change what you can qualify for?
A cosigner can add income and assets to your file. But the rules also add limits you would not face on your own.
On Fannie Mae loans run through Desktop Underwriter (DU): DU looks at the income, assets, debts and credit of every borrower, whether or not they live in the home. When a non-occupying cosigner or co-borrower is on the loan, the maximum loan-to-value ratio is 95%, according to section B2-2-04. That means at least 5% down, before any Community Seconds exception.
On manually underwritten Fannie Mae loans, the rules are tighter when the cosigner's income is used to qualify:
The maximum loan-to-value ratio is 90%.
The buyer living in the home must usually pay the first 5% of the down payment from their own money. Exceptions include a loan-to-value ratio of 80% or less, or a one-unit home where gift, grant or employer money rules are met.
Using only the income of the buyer who will live there, the debt-to-income ratio can be no more than 43%. Fannie Mae says this applies even if the combined ratios look much better.
On FHA loans, HUD Handbook 4000.1 says the maximum loan-to-value ratio for a non-occupying borrower transaction is 75%. It can go up to 96.5% when the borrowers are family members, except when a family member is selling to a family member who will be a non-occupying co-borrower, or when the home has two to four units.
Fannie Mae vs. FHA cosigner rules at a glance
Rule | Fannie Mae (Selling Guide B2-2-04) | FHA (HUD Handbook 4000.1) |
|---|---|---|
Cosigner owns the home? | No ownership on title | No ownership interest |
Non-occupant co-borrower on title? | May or may not be | Must take title |
Builder, seller or real estate agent allowed to help? | No | No, unless a family member exception applies |
Max loan-to-value with a non-occupant helper | 95% in DU; 90% if manually underwritten | 75%; up to 96.5% for family members |
Credit score used | DU reviews every borrower | The lowest decision score of all borrowers |
Sources: Fannie Mae Selling Guide B2-2-04 (dated Sept. 2, 2020) and HUD Handbook 4000.1 (last revised Aug. 12, 2026), both checked Oct. 26, 2026.
Does a cosigner's credit score matter?
Yes. On FHA loans it can matter a lot. HUD Handbook 4000.1 says that when a loan has more than one borrower, the lender finds the decision credit score for each person and then uses the lowest one for the loan. FHA's minimum eligible decision score is 500.
So a cosigner with strong income but a weaker score than yours can pull the whole loan down to their score. Ask your lender to pull both credit reports before you decide who should be on the loan. Our guide to the credit score needed to buy a house explains how scores are chosen.
What does cosigning do to the cosigner?
This is the part families should talk about at the kitchen table first.
A cosigner is legally responsible for the full debt. If the buyer misses payments, the lender can look to the cosigner. The loan can also affect the cosigner's own future borrowing.
Fannie Mae's Selling Guide (section B3-6-05, dated Aug. 5, 2026) explains how a lender treats a mortgage the cosigner signed but someone else pays. The lender may leave that housing payment out of the cosigner's debt-to-income ratio only if:
the person making the payments is also obligated on that mortgage,
there are no late payments in the most recent 12 months, and
the lender gets 12 months of canceled checks or bank statements from the person paying.
Until that 12-month record exists, a cosigner who wants to buy or refinance their own home may see the cosigned payment counted against them. Our guide to the debt-to-income ratio for a mortgage shows how that math works.
Is a cosigner better than a gift?
Not always. If the real problem is cash for the down payment, a family gift may solve it without putting anyone else on the loan. A cosigner mainly helps with income or debt-to-income ratio. Fannie Mae and FHA each have rules for gift money, which we cover in our guide to the mortgage gift letter.
Before choosing, ask your lender to run your file both ways. Getting pre-approved for a mortgage early shows which one actually moves the numbers.
What this means for new-construction buyers
The builder can't be your cosigner. Fannie Mae and FHA both bar the builder, the seller and the real estate agent from cosigning. On FHA, a family-member exception can apply. Keep your helper independent from the sale.
A long build means a long commitment. On a to-be-built home, months can pass between signing the contract and closing. Your lender may ask your cosigner for updated documents before closing, so make sure they know the build timeline and are ready to help.
Plan for the cosigner's own life. If your cosigner plans to buy, sell or refinance during your build, talk to a loan officer about how the new loan will show up on their side.
Ask which loan program fits. FHA's family-member rule (up to 96.5% loan-to-value) and Fannie Mae's DU rule (up to 95%) can lead to different down payments for the same family. Our FHA vs. conventional loan guide compares the two.
Common Questions
Can a parent cosign a mortgage?
Yes. Fannie Mae and FHA both allow cosigners and non-occupant co-borrowers. On FHA loans, the loan-to-value ratio can go up to 96.5% when the borrowers are family members, compared with 75% otherwise.
Is a cosigner on the title of the house?
A cosigner signs the note but does not have an ownership interest on the title. A non-occupant co-borrower is different: on FHA loans they must take title, and on Fannie Mae loans they may or may not be on title.
Can my builder or real estate agent cosign my mortgage?
No. Fannie Mae says a cosigner cannot have an interest in the sale, such as the seller, the builder or the real estate agent. FHA has the same rule, with exceptions when that party is a family member.
Whose credit score is used when there is a cosigner?
On FHA loans, HUD says the lender uses the lowest decision credit score among all borrowers. Fannie Mae's Desktop Underwriter reviews the credit of every borrower on the loan.
Does cosigning a mortgage affect the cosigner's ability to borrow?
It can. Fannie Mae lets a lender leave a cosigned mortgage payment out of the cosigner's debt-to-income ratio only if the other person is also on that mortgage, has 12 months of on-time payments, and the lender gets 12 months of canceled checks or bank statements.
How much do I need to put down with a cosigner?
It depends on the loan. Fannie Mae caps the loan-to-value ratio at 95% in Desktop Underwriter and 90% on manually underwritten loans when a non-occupant helps. FHA allows up to 96.5% for family members and 75% otherwise.
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Related reading: Credit score needed to buy a house · FHA vs. conventional loan · Debt-to-income ratio for a mortgage
Sources: Fannie Mae Selling Guide B2-2-04 · Fannie Mae Selling Guide B3-6-05 · HUD Handbook 4000.1
This is general information, not financial, tax or legal advice. Figures checked October 26, 2026.