GDS/TDS Ratios Explained

Tim Lyon • November 16, 2023

One of the major qualifiers lenders look at when considering your application for mortgage financing is your debt service ratios.


Now, before we get started, if you prefer to have someone walk through these calculations with you, assess your financial situation, and let you know exactly where you stand, let’s connect. There is no use in dusting off the calculator and running the numbers yourself when we can do it for you!


However, if you’re someone who likes to know the nitty-gritty of how things work instead of simply accepting that's just the way it is, this article is for you. But be warned, there are a lot of mortgage words and some math ahead; with that out of the way, let’s get started!

 

“Debt servicing” is the measure of your ability to meet all of your financial obligations. There are two ratios that lenders examine to determine whether you can debt service a mortgage.


The first is called the “gross debt service” ratio, or GDS, which is the percentage of your monthly household income that covers your housing costs. The second is called the “total debt service” ratio, or TDS, which is the percentage of your monthly household income covering your housing costs and all your other debts.


GDS is your income compared to the cost of financing the mortgage, including your proposed mortgage payments (principal and interest), property taxes, and heat (PITH), plus a percentage of your condo fees (if applicable).


Here’s how to calculate your GDS.


Principal + Interest + Taxes + Heat / Gross Annual Income


Your TDS is your income compared to your GDS plus the payments made to service any existing debts. Debts include car loans, line of credit, credit card payments, support payments, student loans, and anywhere else you’re contractually obligated to make payments.


Here’s how to calculate your TDS.


Principal + Interest + Taxes + Heat + Other Debts / Gross Annual Income


With the calculations for those ratios in place, the next step is to understand that each lender has guidelines that outline a maximum GDS/TDS. Exceeding these guidelines will result in your mortgage application being declined, so the lower your GDS/TDS, the better.


If you don’t have any outstanding debts, your GDS and TDS will be the same number. This is a good thing!


The maximum ratios vary for conventional mortgage financing based on the lender and mortgage product being offered. However, if your mortgage is high ratio and mortgage default insurance is required, the maximum GDS is 39% with a maximum TDS of 44%.


So how does this play out in real life? Well, let’s say you’re currently looking to purchase a property with a payment of $1700/mth (PITH), and your total annual household income is $90,000 ($7500/mth). The calculations would be $1700 divided by $7500, which equals 0.227, giving you a gross debt service ratio of 22.7%.


A point of clarity here. When calculating the principal and interest portion of the payment, the Government of Canada has instituted a stress test. It requires you to qualify using the government's qualifying rate (which is higher), not the actual contract rate. This is true for both fixed and variable rate mortgages.


Now let’s continue with the scenario. Let’s say that in addition to the payments required to service the property, you have a car payment of $300/mth, child support payments of $500/mth, and between your credit cards and line of credit, you’re responsible for another $700/mth. In total, you pay $1500/mth. So when you add in the $1700/mth PITH, you arrive at a total of $3200/mth for all of your financial obligations. $3200 divided by $7500 equals 0.427, giving you a total debt service ratio of 42.7%.


Here’s where it gets interesting. Based on your GDS alone, you can easily afford the property. But when you factor in all your other expenses, the TDS exceeds the allowable limit of 42% (for an insured mortgage anyway). So why does this matter? Well, as it stands, you wouldn’t qualify for the mortgage, even though you are likely paying more than $1700/mth in rent.


So then, to qualify, it might be as simple as shuffling some of your debt to lower payments. Or maybe you have 10% of the purchase price saved for a downpayment, changing the mortgage structure to 5% down and using the additional 5% to pay out a portion of your debt might be the difference you need to bring it all together.


Here’s the thing, as your actual financial situation is most likely different than the one above, working with an independent mortgage professional is the best way to give yourself options. Don’t do this alone. Your best plan is to seek and rely on the advice provided by an experienced independent mortgage professional. While you might secure a handful of mortgages over your lifetime, we do this every day with people just like you.


It’s never too early to start the conversation about mortgage qualification. Going over your application and assessing your debt service ratios in detail beforehand gives you the time needed to make the financial moves necessary to put yourself in the best financial position.


So if you find yourself questioning what you can afford or if you want to discuss your GDS/TDS ratios to understand the mortgage process a little better, please get in touch. It would be a pleasure to work with you, we can get a preapproval started right away.

Tim Lyon

Mortgage Consultant

Credit and Mortgage Financing

By Tim Lyon • October 9, 2025
Credit. The ability of a customer to obtain goods or services before payment, based on the trust that you will make payments in the future. When you borrow money to buy a property, you’ll be required to prove that you have a good history of managing your credit. That is, making good on all your payments. But what exactly is a “good history of managing credit”? What are lenders looking at when they assess your credit report? If you’re new to managing your credit, an easy way to remember the minimum credit requirements for mortgage financing is the 2/2/2 rule. Two active trade lines established over a minimum period of two years, with a minimum limit of two thousand dollars, is what lenders are looking for. A trade line could be a credit card, an instalment loan, a car loan, or a line of credit; basically, anytime a lender extends credit to you. Your repayment history is kept on your credit report and generates a credit score. For a tradeline to be considered active, you must have used it for at least one month and then once every three months. To build a good credit history, both of your tradelines need to be used for at least two years. This history gives the lender confidence that you’ve established good credit habits over a decent length of time. Two thousand dollars is the bare minimum limit required on your trade lines. So if you have a credit card with a $1000 limit and a line of credit with a $2500 limit, you would be okay as your limit would be $3500. If you’re managing your credit well, chances are you will be offered a limit increase. It’s a good idea to take it. Mortgage Lenders want to know that you can handle borrowing money. Now, don’t confuse the limit with the balance. You don’t have to carry a balance on your trade lines for them to be considered active. To build credit, it’s best to use your tradelines but pay them off in full every month in the case of credit cards and make all your loan payments on time. A great way to use your credit is to pay your bills via direct withdrawal from your credit card, then set up a regular transfer from your bank account to pay off the credit card in full every month. Automation becomes your best friend. Just make sure you keep on top of your banking to ensure everything works as it should. Now, you might be thinking, what about my credit score, isn’t that important when talking about building a credit profile to secure a mortgage? Well, your credit score is important, but if you have two tradelines, reporting for two years, with a minimum limit of two thousand dollars, without missing any payments, your credit score will take care of itself, and you should have no worries. With that said, it never hurts to take a look at your credit every once and a while to ensure no errors are reported on your credit bureau. So, if you’re thinking about buying a property in the next couple of years and want to make sure that you have good enough credit to qualify, let’s talk. Connect anytime; it would be a pleasure to work with you and help you to understand better how your credit impacts mortgage qualification.

How Mortgage Rates Work: Fixed vs. Variable

By Tim Lyon • September 26, 2025
What affects mortgage rates? Does the Bank of Canada rate affect fixed-rate mortgages? These are questions that come up all the time, so in this this post, I’ll explain how fixed and variable rates are determined, why they don’t always move together, and what that means for you as a borrower. But to start with the short answer: While Bank of Canada announcements immediately impact variable rates, fixed rates usually have those expectations already baked in long before the announcement. That’s because fixed rates are forward-looking — they reflect where markets think rates are headed, not just where they are today. What Are Fixed and Variable Rates? Fixed Rate The interest rate stays the same for the entire mortgage term. Payments remain consistent, no matter what happens in the market. Variable Rate The interest rate changes during the mortgage term, moving up or down depending on the lender’s prime rate. Payments may stay the same (VRM) or change (ARM). How Do Fixed Rates Work? When you choose a fixed rate, the lender is guaranteeing your rate for the length of your term . To do this, they need to estimate what a fair rate will be over that time. This makes fixed rates more forward-looking — they often reflect not just today’s conditions, but also what the market expects to happen in the future. Key Points About Fixed Rates Strongly influenced by the Canadian bond market (especially the 5-year government bond yield). Lenders adjust their fixed rates based on investor expectations for inflation and future interest rates. Often, Bank of Canada moves are already baked into fixed rates before they happen. Example If bond yields suggest that rates will rise in the next year, lenders may increase fixed rates now, even if the Bank of Canada hasn’t made a move yet. How Do Variable Rates Work? Variable rates move directly with the Bank of Canada’s overnight rate. When the Bank of Canada raises or lowers its rate, lenders adjust their prime rate accordingly, and variable mortgages follow. For borrowers, the most important detail is the discount from prime , because that sets the actual rate you pay. For example, if prime is 4.95% and your mortgage is Prime – 0.5%, your rate is 4.45%. The discounts lenders offer change over time. In periods of economic uncertainty, lenders usually shrink the discount they offer, which can make new variable mortgages less attractive even if prime is coming down. Key Points About Variable Rates Directly tied to the Bank of Canada’s overnight rate, which is reviewed eight times a year. Banks adjust their prime rate in response to these moves. Your actual rate = Prime – discount (e.g., Prime – 0.5%). Example If prime is 4.95% and your mortgage is Prime – 0.5%, your rate is 4.45%. If the Bank of Canada cuts rates by 0.25%, prime drops to 4.70%, and your rate automatically drops to 4.20%. Why Don’t Fixed and Variable Always Move Together? Fixed rates reflect the bond market, which looks ahead at where rates and inflation may go. Variable rates respond directly to Bank of Canada decisions, reflecting current conditions. This is why fixed rates can fall while variable rates stay flat, or vice versa. Next Steps If you’re deciding between fixed and variable, understanding how each is set is the first step. The next is to match the right mortgage type to your budget and comfort with risk. If you’d like to review which option works best for you, I’d be happy to help. Need help with your mortgage? Book a consultation or call 778-988-8409 . Mortgage Term Glossary Amortization: The total length of time it will take to pay off your mortgage completely (typically 25–30 years in Canada). Bond Yield: The return investors get from government bonds. Used as a benchmark for fixed mortgage rates. Discount (Variable Rate): The amount subtracted from prime to determine your actual mortgage rate. Fixed Rate: An interest rate that stays the same for the entire mortgage term. Mortgage Term: The length of your mortgage contract with your lender (typically 1–5 years), after which you need to renew. Overnight Rate: The interest rate at which major banks borrow and lend money to each other, set by the Bank of Canada. Prime Rate: The interest rate banks use as a baseline for loans, influenced by the Bank of Canada’s overnight rate. Variable Rate: An interest rate that changes during your mortgage term based on lender prime rates.