What Are GDS/TDS Ratios Anyways?

Bill Fraser • April 18, 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.


BILL FRASER
OWNER / MORTGAGE EXPERT

BOOK AN APPOINTMENT CONTACT ME
RECENT POSTS

Mortgages Aren’t One-Size-Fits-All

By Bill Fraser • December 9, 2025
Why the Cheapest Mortgage Isn’t Always the Smartest Move Some things are fine to buy on the cheap. Generic cereal? Sure. Basic airline seat? No problem. A car with roll-down windows? If it gets you where you're going, great. But when it comes to choosing a mortgage? That’s not the time to cut corners. A “no-frills” mortgage might sound appealing with its rock-bottom interest rate, but what’s stripped away to get you that rate can end up costing you far more in the long run. These mortgages often come with severe limitations—restrictions that could hit your wallet hard if life throws you a curveball. Let’s break it down. A typical no-frills mortgage might offer a slightly lower interest rate—maybe 0.10% to 0.20% less. That could save you a few hundred dollars over a few years. But that small upfront saving comes at the cost of flexibility: Breaking your mortgage early? Expect a massive penalty. Want to make extra payments? Often not allowed—or severely restricted. Need to move and take your mortgage with you? Not likely. Thinking about refinancing? Good luck doing that without a financial hit. Most people don’t plan on breaking their mortgage early—but roughly two-thirds of Canadians do, often due to job changes, separations, relocations, or expanding families. That’s why flexibility matters. So why do lenders even offer no-frills mortgages? Because they know the stats. And they know many borrowers chase the lowest rate without asking what’s behind it. Some banks count on that. Their job is to maximize profits. Ours? To help you make an informed, strategic choice. As independent mortgage professionals, we work for you—not a single lender. That means we can compare multiple products from various financial institutions to find the one that actually suits your goals and protects your long-term financial health. Bottom line: Don’t let a shiny low rate distract you from what really matters. A mortgage should fit your life—not the other way around. Have questions? Want to look at your options? I’d be happy to help. Let’s chat.

Collateral vs. Standard Mortgage: Pros and Cons Explained

By Bill Fraser • December 2, 2025
Mortgage Registration 101: What You Need to Know About Standard vs. Collateral Charges When you’re setting up a mortgage, it’s easy to focus on the rate and monthly payment—but what about how your mortgage is registered? Most borrowers don’t realize this, but there are two common ways your lender can register your mortgage: as a standard charge or a collateral charge . And that choice can affect your flexibility, future borrowing power, and even your ability to switch lenders. Let’s break down what each option means—without the legal jargon. What Is a Standard Charge Mortgage? Think of this as the “traditional” mortgage. With a standard charge, your lender registers exactly what you’ve borrowed on the property title. Nothing more. Nothing hidden. Just the principal amount of your mortgage. Here’s why that matters: When your mortgage term is up, you can usually switch to another lender easily —often without legal fees, as long as your terms stay the same. If you want to borrow more money down the line (for example, for renovations or debt consolidation), you’ll need to requalify and break your current mortgage , which can come with penalties and legal costs. It’s straightforward, transparent, and offers more freedom to shop around at renewal time. What Is a Collateral Charge Mortgage? This is a more flexible—but also more complex—type of mortgage registration. Instead of registering just the amount you borrow, a collateral charge mortgage registers for a higher amount , often up to 100%–125% of your home’s value . Why? To allow you to borrow additional funds in the future without redoing your mortgage. Here’s the upside: If your home’s value goes up or you need access to funds, a collateral charge mortgage may let you re-borrow more easily (if you qualify). It can bundle other credit products—like a line of credit or personal loan—into one master agreement. But there are trade-offs: You can’t switch lenders at renewal without hiring a lawyer and paying legal fees to discharge the mortgage. It may limit your ability to get a second mortgage with another lender because the original lender is registered for a higher amount than you actually owe. Which One Should You Choose? The answer depends on what matters more to you: flexibility in future borrowing , or freedom to shop around for better rates at renewal. Why Talk to a Mortgage Broker? This kind of decision shouldn’t be made by default—or by what a single lender offers. An independent mortgage professional can help you: Understand how your mortgage is registered (most people never ask!) Compare lenders that offer both options Make sure your mortgage aligns with your future goals—not just today’s needs We look at your full financial picture and explain the fine print so you can move forward with confidence—not surprises. Have questions? Let’s talk. Whether you’re renewing, refinancing, or buying for the first time, I’m here to help you make smart, informed choices about your mortgage. No pressure—just answers.