A mortgage pre-approval is the first piece of real information you get about what you can actually buy. It is also the most widely misunderstood document in the process, because the number on it looks like a promise and is not one.
Two things are worth being clear about before anything else. The federal consumer agency states it plainly: the pre-approval process "does not guarantee your approval for a mortgage". And the maximum on the page is a ceiling set by a formula, not a recommendation about what you should spend.
What a pre-approval actually gives you
Three things, according to the Financial Consumer Agency of Canada. It tells you the maximum amount of a mortgage you could qualify for. It lets you estimate your payments. And it locks in an interest rate for 60 to 130 days, depending on the lender.
That range matters. Most articles on this subject quote a flat 90 or 120 days. The actual window varies by lender, and the difference between 60 and 130 days is the difference between a comfortable search and a rushed one in a market where the right home takes a while to appear.
You may also see the same thing called prequalification or preauthorization. Lenders use these words differently and there is no standard industry definition, so the label tells you less than the terms do. Ask what the rate hold is and what conditions apply rather than relying on which of the three words appears at the top of the page.
The two ratios that decide your number
This is the part almost no consumer page explains, and it is the mechanism behind every pre-approval figure ever issued. Lenders apply two debt service ratios.
Gross Debt Service, capped at 39 per cent
Your total monthly housing costs should not exceed 39 per cent of your gross household income. Gross means before tax, which is why the number feels generous until you do the arithmetic on your actual take-home pay.
Four things count toward it:
- your mortgage payments
- your property taxes
- your heating costs
- 50 per cent of your condo fees, if you have them
The condo fee rule catches Calgary buyers out regularly. Half of your monthly fee is treated as a housing cost, so a $600 monthly fee consumes $300 of your GDS room before you have borrowed a dollar. On an apartment purchase that is often the difference between qualifying and not.
Total Debt Service, capped at 44 per cent
Your total debt load should not exceed 44 per cent of your gross income. This is your housing costs plus everything else you owe monthly: credit card balances, car loans, lines of credit, student loans, child or spousal support, and any other debts.
The gap between the two ratios is only five percentage points, and that gap is all the room you have for every non-housing debt you carry. A car payment of a few hundred dollars a month can reduce your maximum mortgage by tens of thousands. Paying down or clearing a car loan before you apply frequently does more for your buying power than saving the equivalent amount toward the down payment.
Then the stress test reduces it again
Having good ratios at your actual interest rate is not enough. Federally regulated lenders must qualify you at a higher rate than the one you are being offered, which the Office of the Superintendent of Financial Institutions calls the minimum qualifying rate.
The rule is the greater of your contract rate plus two per cent, or 5.25 per cent. If your lender offers 4.4 per cent, your ratios have to work at 6.4 per cent. If you are offered 3 per cent, the 5.25 per cent floor applies instead.
OSFI describes these as two components: a buffer, currently two per cent, and a floor, currently 5.25 per cent. Both are reviewed at least once a year, so neither is permanent. The purpose is to establish that you could still pay if rates rose or your income fell.
This is the single most common reason a buyer is approved for less than they expected. Your budget is not being assessed at the rate you will actually pay.
What to bring
A lender or broker looks at three things: your assets, your income, and your level of debt. You will need to provide identification, proof of employment, proof that you can cover the down payment and closing costs, information about other assets such as a car or a second property, and information about your debts.
For proof of employment, expect to show current salary or hourly rate, usually a recent pay stub, along with your position and how long you have been with the employer.
If you are self-employed, you will be asked for notices of assessment from the Canada Revenue Agency for the past two years. This is worth planning around in a province with as much self-employment as Alberta, particularly if you write off aggressively. Lenders assess the income you declared, not the income you earned, and the two can differ substantially for a contractor or a small business owner.
What about credit scores
You will find a specific minimum score quoted almost everywhere, most often 680. The federal consumer agency publishes no such threshold. What it says is that without a good credit score a lender may refuse to approve your mortgage, or may require someone to co-sign.
There is no single national minimum because each lender sets its own guidelines. A score that one lender declines, another may accept at a higher rate. If your credit is the weak part of your application, that is a reason to talk to a broker who deals with several lenders rather than to assume you are excluded by a number you read online.
Why a pre-approved buyer can still be refused
This is the part that costs people deals, and it comes down to a distinction that is easy to miss. Your pre-approval assessed you. Final approval assesses the property as well.
Before a lender approves the loan, it verifies that the specific home meets its standards, and those standards vary from lender to lender. If the appraisal comes in below the purchase price, if the property has issues the lender considers unacceptable, or if it is a type of property that lender does not like, you can be refused on that home while remaining perfectly qualified for another.
The other reason is that your own circumstances changed. A pre-approval is a snapshot. Changing jobs, taking on a car loan, or opening a new credit line between pre-approval and closing can undo it. The safest rule between pre-approval and possession is to change nothing about your finances at all.
If you are refused, the lender may still offer alternatives: approving a lower mortgage amount, charging a higher interest rate, requiring a larger down payment, or requiring a co-signer.
This is also the reason a financing condition matters. An offer that is not subject to financing leaves you personally liable for a purchase your lender has declined to fund, and a pre-approval letter is not a defence.
Lender or broker
Mortgage lenders lend you money directly. They include banks, credit unions, caisses populaires, mortgage companies, insurance companies, trust companies and loan companies.
Mortgage brokers do not lend. They arrange the transaction by finding a lender for you. Some products are only sold directly by lenders and some are only available through brokers, so the two routes do not reach the same set of options.
Brokers generally do not charge you a fee. They are paid a commission by the lender when the deal completes. That is worth understanding rather than worrying about: it means the service is usually free to you, and it also means you should ask which lenders a particular broker works with, because brokers do not all have access to the same ones.
Mortgage brokers are regulated provincially, not federally. In Alberta that is the Real Estate Council of Alberta, and you can confirm that a broker is licensed or make a complaint through the provincial regulator.
Questions worth asking
The federal consumer agency suggests three, and they are better than the questions most buyers ask:
- How long is the pre-approved rate guaranteed for?
- If interest rates go down while you are pre-approved, do you automatically get the lower rate?
- Can the pre-approval be extended?
The second is the one people forget. Some lenders pass on a drop automatically and some do not, and over a four-month hold that can be worth a great deal of money.
Treat the maximum as a ceiling, not a target
The pre-approval amount is the most a lender may give you. It is not advice about what you should spend, and the ratios that produced it do not know what your life costs.
The formula counts your mortgage, property taxes, heating and half your condo fees. It does not count childcare, vehicle running costs, savings, or the fact that a house needs a new roof every twenty years. It also does not include the closing costs, moving costs and ongoing maintenance that arrive whether you budgeted for them or not.
Buying below your maximum is not a failure of ambition. In a market where the Calgary benchmark price sat at $569,800 in August 2026, the difference between buying at your ceiling and buying $50,000 under it is the difference between a mortgage that survives a bad year and one that does not.