If someone has asked you to co-sign their mortgage, it likely means they trust you deeply — and that you’re in a strong enough financial position to help them qualify. But before you say yes, it’s worth understanding exactly what co-signing a mortgage in Canada involves, because the risks go further than most people expect.

In Calgary and across Alberta, more families are using co-signing arrangements to help first-time buyers get into the market. While it can absolutely be the right move, everyone needs to go in with eyes wide open.

What Does Co-Signing a Mortgage Actually Mean?

When you co-sign a mortgage in Canada, you take on full legal responsibility for the loan alongside the primary borrower. You’re not responsible for a portion of it — you’re on the hook for 100% of the debt if the primary borrower can’t make payments.

In most cases, lenders also add co-signers to the property title. That makes you a part-owner of the home — even if you don’t live there and contribute nothing to the day-to-day costs.

The Risks of Co-Signing a Mortgage in Canada

1. It immediately affects your borrowing power

The moment you co-sign, that full mortgage payment counts as your debt obligation on your credit bureau. This can reduce your ability to qualify for future credit — whether that’s a refinance, a HELOC, a car loan, or helping another family member down the road. The full mortgage payment is included in the co-signer’s debt obligations, which can limit their ability to qualify for future credit. Nesto

2. Getting off the mortgage is harder than getting on

You can’t simply call your lender and ask to be removed. The primary borrower has to requalify on their own first, and the lender must approve the change. Some lenders charge a fee to update the mortgage documents, so understanding your lender’s terms before bringing on a co-signer is important. NerdWallet

There’s another wrinkle worth knowing: at several major lenders in Canada, only one person listed on the mortgage needs to sign for a renewal to take effect. Canadian Mortgage Trends A co-signer could be locked in for another full term without being directly involved in the decision.

3. Missed payments hurt your credit too

If payments are missed, both the borrower’s and co-signer’s credit histories are impacted. Nesto Even if you’re making no payments and have no day-to-day involvement in the property, a late payment from the primary borrower shows up on your credit report as well.

4. There can be tax implications

Because lenders typically add co-signers to the property title, the CRA may treat you as a partial owner. That can mean capital gains tax exposure when the property sells — even if your ownership stake is minor – if the property wasn’t the principal residence of the primary borrower. As of the 2025 tax year, bare trusts must be reported to the CRA, and if you’re part of a bare trust agreement — such as a co-signing arrangement — you may need to file a T3 Trust Income Tax and Information Return. ASK ROSS

Co-Signer vs. Guarantor: Is There a Difference?

Yes — and it matters. A co-signer goes on the property title, while a guarantor supports the application without appearing on title. Fewer lenders allow guarantor arrangements today — most want all parties on the title. ASK ROSS Credit unions tend to offer more flexibility here than chartered banks.

Before You Co-Sign, Ask These Questions

  • Can the primary borrower realistically afford this mortgage on their own over time?
  • What is the plan for eventually removing you from the mortgage?
  • Have you spoken with a mortgage broker, a tax accountant, and a real estate lawyer?
  • How does this affect your own financial plans — including retirement or helping other family members?

The Bottom Line on Co-Signing a Mortgage in Canada

Co-signing a mortgage in Canada is a generous act. In the right circumstances, it can be exactly what a family member needs to get into their first home. But it’s a long-term financial commitment that deserves careful thought and professional advice before you move forward.

If you’re in Calgary or anywhere in Alberta and want to talk through whether co-signing makes sense for your situation — reach out. These are exactly the conversations I’m here for.

Book a call with Sue!