How Co-Signing a Loan Affects Buying a House

Co-signing a loan can directly reduce how much house you qualify for, because the co-signed debt’s monthly payment is usually added to your debt-to-income (DTI) ratio even when someone else makes the payments. When you co-sign, a lender treats the obligation as yours until you can prove otherwise. That means a car loan, student loan, or credit line you signed for as a favor can quietly shrink your buying power years later, and any late payment the other person makes can land on your credit report. The good news: the same agencies that set these rules also spell out a clear path to remove the debt from the equation before you apply for a mortgage.

What co-signing actually commits you to

Co-signing is not a character reference. It is a legal promise to repay someone else’s debt in full if they do not. The Consumer Financial Protection Bureau (CFPB) is blunt about the scope of that promise: as a co-signer, “you may have to pay up to the full amount of the debt if the borrower does not pay,” and “the creditor can collect this debt from you without first trying to collect from the borrower.”

In practical terms, you carry the same liability as the primary borrower even though you may own none of what the loan bought. The lender does not have to exhaust its options with the other person first. It can come straight to you. The CFPB also warns that “any missed payments could also appear on your credit reports and impact your credit scores, making it harder for you to get credit in the future.” For anyone planning to buy a home, that last sentence is the whole ballgame.

How co-signing lowers the house you qualify for

Mortgage approval turns heavily on your debt-to-income ratio, the share of your gross monthly income eaten by required debt payments. Every monthly obligation on your credit report is a candidate for that calculation, and a co-signed loan shows up as your obligation because, legally, it is.

Consider a straightforward example. Say you earn $6,000 a month and already carry $1,800 in monthly debt payments, putting your DTI at 30%. You co-signed your nephew’s $400-a-month car loan two years ago. Unless you can document that he has been paying it, the underwriter adds that $400 to your side of the ledger. Your qualifying debt jumps to $2,200 and your DTI climbs to roughly 37%. That single number can be the difference between a comfortable approval and a declined file, or between the loan amount you wanted and a smaller one.

The co-signed payment counts against you by default. Getting it excluded is something you have to prove, with documents, not something the underwriter assumes in your favor.

What the mortgage rulebooks say about co-signed debt

This is not lender preference or one loan officer’s opinion. It is written into the guidelines the entire industry follows. All three major rulebooks treat a debt you co-signed as your debt unless a specific documentation test is met.

Fannie Mae’s Selling Guide addresses this under “Debts Paid by Others.” A monthly obligation can be excluded from your DTI only if another party has been making the payments and you can document it. The rule requires the lender to “obtain the most recent 12 months’ canceled checks (or bank statements) from the other party making the payments that document a 12-month payment history with no delinquent payments.” Miss any part of that, and the payment stays in your ratio.

Freddie Mac’s Seller/Servicer Guide sets an equivalent bar: where another party has paid a non-mortgage debt, it may be excluded when that party “has been paying the entire monthly payment for a minimum of 12 months,” documented with twelve months of canceled checks or bank statements. For FHA loans, HUD Handbook 4000.1 says lenders must include contingent-liability payments in your obligations unless there is proof the debt holder will not pursue you, or “the other legally obligated party has made 12 months of timely payments.” The common thread across conventional and government financing is the same:

• Default treatment: the co-signed payment counts in your DTI.
• The escape hatch: 12 months of on-time payments made by the other party.
• The proof: 12 months of canceled checks or bank statements from that party, showing no late payments.

Note one nuance underwriters watch: a source paying the debt cannot be an interested party to your home purchase (for example, the seller), and for a co-signed mortgage there generally cannot be any 30-day-plus late payments in the most recent 12 months. If you are self-employed and your income picture is already nuanced, this documentation step deserves extra lead time; our self-employed mortgage guide walks through how underwriters build the full picture.

The credit-score risk is separate and immediate

DTI is only half the problem. Because a co-signed account reports on your credit file, the primary borrower’s behavior becomes your credit history. If they pay 30 days late, that late payment can post to your reports and drag your scores down, exactly when you need them steady for a mortgage. A single serious late payment can cost meaningful points and can matter more than months of on-time history, which is why we cover it in depth in late payments and your mortgage.

There is a second, quieter drag. A co-signed revolving account that runs a high balance can push your overall utilization up, and utilization is one of the biggest movable factors in a score. If the card you co-signed sits near its limit, that alone can weigh on you; we explain the mechanics in credit utilization before a mortgage. The uncomfortable reality is that you can do everything right on your own accounts and still watch your score slip because of an account you do not control.

Co-signer vs. co-borrower vs. authorized user

These three roles get lumped together in conversation, but they carry very different liability and scoring effects. Knowing which one you agreed to tells you exactly how it will hit a mortgage application.

• Co-signer: fully liable for the whole debt, no ownership of what it bought, and the payment counts in your DTI by default. This is the role this article is about.
• Co-borrower: jointly and severally liable and typically an owner. On a mortgage, a co-borrower’s income and debts are underwritten right alongside yours from day one.
• Authorized user: permitted to use the account but, under federal law, not obligated to repay it. The card issuer, not the authorized user, owes the balance.

The authorized-user distinction matters for scoring. According to myFICO, “authorized user accounts have less impact to your FICO Score than primary accounts” in recent score versions, though the account can still appear on your report and affect the score in both directions. Compare that to co-signing, where you are on the hook for every dollar. Being added as an authorized user is a common, low-risk way to build credit on a thin file; co-signing is a full liability. They are not the same favor.

How to get out from under a co-signed loan before you buy

If you co-signed something and now want to buy a home, you have concrete options. Work through them in order of cleanliness:

1. Document 12 months of on-time payments by the other party. If your nephew, sibling, or friend has genuinely been paying, gather 12 months of their canceled checks or bank statements showing on-time payments. Under Fannie Mae, Freddie Mac, and FHA rules, that lets the underwriter exclude the payment from your DTI. This is the fastest fix when the payment record is clean.
2. Refinance the loan out of your name. If the primary borrower now qualifies on their own, having them refinance removes you as an obligor entirely. The debt disappears from your credit report and your DTI, and you are no longer exposed to their future late payments.
3. Pay it off or have it paid off before closing. If the balance is small, retiring it removes the payment from your ratio. Coordinate timing with your loan officer so the paid-off status is documented correctly.
4. Qualify with the payment included. If the numbers still work with the co-signed payment in your DTI, you may simply proceed. An honest pre-approval will tell you whether you have room.

Which path fits depends on the loan type, the payment history, and how soon you want to buy. A broker can model each scenario against real guidelines before you commit to one. As an independent mortgage broker in Colorado Springs, we shop your file across multiple wholesale lenders, which matters when a co-signed debt puts you near a DTI threshold and one investor’s overlay is stricter than another’s.

Our take: talk to a loan officer before you co-sign

In our experience at 719 Lending, the co-signing problems we see are almost never about the borrower who defaulted. They are about a well-meaning person who co-signed years ago, forgot about it, and then discovered at pre-approval that a debt they never think about is capping their loan amount. Our take: if you plan to buy a home within the next couple of years, treat co-signing anything as a decision that touches your own mortgage, and talk it through with a loan officer first. A ten-minute conversation before you sign is far cheaper than restructuring a debt in the middle of an escrow.

The same logic applies when the co-signed obligation is tangled up with a partner’s finances. If you are buying with a spouse, both credit profiles come into play in ways many buyers do not expect, which we cover in how your spouse’s credit score affects your mortgage. And if you are still early in the process and unsure what score you actually need, start with our pillar overview of what credit score you need to buy a house.

Frequently asked questions

Does co-signing a loan hurt my chances of buying a house? It can. By default the co-signed monthly payment is added to your debt-to-income ratio, which lowers how much home you qualify for, and any late payment by the primary borrower can also lower your credit scores. You can remove the DTI hit by documenting 12 months of on-time payments made by the other party, per Fannie Mae, Freddie Mac, and FHA guidelines. Figures are general; confirm current guidelines with a lender.

Can a co-signed debt be excluded from my debt-to-income ratio? Yes, if another party has been making the payments and you can prove it. Fannie Mae and Freddie Mac both require the most recent 12 months of canceled checks or bank statements from the paying party showing a 12-month history with no delinquent payments; FHA allows exclusion when the other legally obligated party has made 12 months of timely payments. Without that documentation, the payment stays in your ratio.

What is the difference between a co-signer and a co-borrower on a mortgage? A co-signer is fully liable for the debt but usually owns none of what it bought, and the payment counts against their DTI by default. A co-borrower shares equal legal responsibility and is typically an owner, and their income and debts are underwritten alongside yours from day one. Both are more exposed than an authorized user, who under federal law is not obligated to repay the account.

Will the primary borrower’s late payments show up on my credit report? Yes. Because a co-signed account reports on your credit file, the primary borrower’s missed or late payments can post to your reports and lower your scores. The CFPB notes that missed payments “could also appear on your credit reports and impact your credit scores.” That is a separate risk from the DTI issue and can affect you even if your own accounts are perfect.

How do I remove myself from a loan I co-signed before buying a home? The cleanest option is to have the primary borrower refinance the loan into their own name, which removes you as an obligor entirely. Alternatively, document 12 months of on-time payments by the other party to exclude it from your DTI, or pay off a small balance before closing. Which route fits depends on the loan type and payment history; a loan officer can model each one.

Is being an authorized user the same as co-signing? No. An authorized user can use an account but is not legally responsible for the balance, while a co-signer is fully liable for the entire debt. Authorized-user accounts also carry less weight in recent FICO score versions than primary accounts, according to myFICO. Co-signing exposes you to the full debt and to the DTI and credit-score effects described above.

719 Lending, NMLS #1601989. Equal Housing Opportunity. 719 Lending is not affiliated with, or acting on behalf of or at the direction of, HUD/FHA, the VA, USDA, CHFA, or any government agency. This article is educational and not a commitment to lend or financial advice. All figures, thresholds, and guidelines are general and subject to change; confirm current requirements with a licensed loan officer. Last updated: June 2026.