Mortgage default insurance protects the lender if a borrower defaults on a high-ratio mortgage. In Canada it is provided by CMHC, a federal Crown corporation, and by private insurers.

Key features of mortgage default insurance in Canada

Feature	What it generally means
Who provides it	CMHC is a federal Crown corporation; private insurers also provide mortgage loan insurance in Canada.
Who it protects	It protects the lender if the borrower defaults, not the borrower or co-signer.
When it is generally used	It is generally associated with high-ratio mortgages, where the down payment is below the threshold set by the lender and insurer.
What it does not do	It does not remove the borrower's or co-signer's obligation to repay the debt.
Effect of a co-signer	A co-signer may help the file qualify, but the lender and insurer still assess the application.

Mortgage default insurance, often called mortgage loan insurance, protects the lender if a borrower defaults on a high-ratio mortgage. In Canada it is provided by the Canada Mortgage and Housing Corporation (CMHC), a federal Crown corporation, and by private insurers. A co-signer can help a borrower qualify for a mortgage, but it does not remove the insurance requirement or change who the insurance protects. This page explains what the insurance does, how a co-signer fits in, and what to confirm before applying.

What mortgage default insurance does

Mortgage default insurance is designed to protect the lender, not the borrower. If a borrower defaults and the lender suffers a loss after the property is dealt with, the insurer may cover part of that loss. Because the insurance reduces the lender's risk, it allows lenders to offer mortgages to buyers who make a smaller down payment than would otherwise be required. The Financial Consumer Agency of Canada covers mortgage basics on its mortgages page, and CMHC publishes its own guidance at cmhc-schl.gc.ca.

It is a common misunderstanding that mortgage default insurance protects the borrower against losing the home. It does not. The borrower and any co-signer remain responsible for the debt. If the home is sold for less than the amount owed, the lender can generally pursue the borrower and the co-signer for the shortfall, subject to the law and the terms of the agreement.

How a co-signer fits into an insured mortgage

A co-signer is typically added to help the application qualify, for example by adding income or strengthening the credit profile. The lender assesses the co-signer as part of the application, and the insurer may also consider the overall file. Being a co-signer on a mortgage is a serious commitment, because a mortgage is a large, long-term debt and the co-signer is generally responsible for it.

Adding a co-signer does not usually remove the need for mortgage default insurance on a high-ratio mortgage. The insurance requirement is tied to the loan and the down payment, not to the number of borrowers. What the co-signer may change is whether the application meets the lender's criteria for income, credit, and debt service. You should confirm with the lender and the insurer how the co-signer will be treated and how the account will be reported.

Key features at a glance

The table on this page summarises the main features in plain language. Details vary by lender and insurer, and the rules can change, so confirm the current requirements with the lender before you rely on any general description.

What lenders and insurers look at

1. The size of the down payment and the resulting loan-to-value ratio.
2. The borrower's and co-signer's income and employment.
3. Credit history and credit scores for everyone on the application.
4. Existing debts and the resulting debt-service calculations.
5. The property itself, including its value and condition.
6. The terms of the mortgage, including amortization and whether the rate is fixed or variable.

What this means for co-signers

Co-signing a mortgage is one of the largest financial commitments a person can make on someone else's behalf. The debt can stay on the co-signer's credit report for years, and it can reduce the co-signer's ability to borrow for their own goals. Before agreeing, ask the lender for the full picture: the loan amount, the payment, the amortization, the insurance premium, and what happens if the borrower defaults. Also ask whether there is any process to be removed later, and get the answer in writing.

• Understand that the insurance protects the lender, not you.
• Confirm how the mortgage will appear on your credit report.
• Ask about the insurance premium and who pays it.
• Do not assume you can be removed once the borrower pays on time.
• Seek independent advice before committing to a large joint mortgage.

Mortgage default insurance is often misunderstood because the word insurance suggests that the borrower is the protected party. In fact, the lender is the beneficiary. The insurance allows lenders to offer high-ratio mortgages, and the cost of the premium is typically passed on to the borrower and added to the loan or paid upfront. A co-signer should understand that the premium exists and who ultimately pays it.

It is also worth distinguishing mortgage default insurance from other products with similar names. Mortgage life insurance, for example, is a separate product that may pay off the mortgage if the insured person dies or becomes disabled. Title insurance is another distinct product that protects against certain title defects. Confusing these products can lead to gaps in coverage or unnecessary cost, so ask the lender to explain exactly what is being provided.

When a co-signer is added, the lender and the insurer generally look at the combined file. The co-signer's income can strengthen the application, but the co-signer's debts can weaken it, and the co-signer's credit history is part of the picture. The lender will also consider the property, the down payment, and the amortization. Because the assessment is holistic, it is worth asking the lender which factors are most important in your case.

For the co-signer, the practical risks are long-term. A mortgage can run for decades, and the co-signer's obligation generally lasts as long as the debt. The co-signer's own ability to borrow may be reduced, because the mortgage may count in their debt-service calculations. If the borrower defaults and the sale proceeds do not cover the debt, the lender may pursue the co-signer. These are serious possibilities, and they deserve careful thought before any commitment.