Mortgage Approval 101: GDS & TDS Explained

Debra Parker • January 20, 2026

Can You Afford That Mortgage? Let’s Talk About Debt Service Ratios

One of the biggest factors lenders look at when deciding whether you qualify for a mortgage is something called your debt service ratios. It’s a financial check-up to make sure you can handle the payments—not just for your new home, but for everything else you owe as well.


If you’d rather skip the math and have someone walk through this with you, that’s what I’m here for. But if you like to understand how things work behind the scenes, keep reading. We’re going to break down what these ratios are, how to calculate them, and why they matter when it comes to getting approved.


What Are Debt Service Ratios?

Debt service ratios measure your ability to manage your financial obligations based on your income. There are two key ratios lenders care about:

  1. Gross Debt Service (GDS)
    This looks at the percentage of your income that would go toward housing expenses only.

   2. Total Debt Service (TDS)
       This includes your housing costs plus all other debt payments—car loans, credit cards, student loans, support payments, etc.


How to Calculate GDS and TDS

Let’s break down the formulas.


GDS Formula:

(P + I + T + H + Condo Fees*) ÷ Gross Monthly Income


Where:

P = Principal

I = Interest

T = Property Taxes

H = Heat


Condo fees are usually calculated at 50% of the total amount


TDS Formula:

(GDS + Monthly Debt Payments) ÷ Gross Monthly Income


These ratios tell lenders if your budget is already stretched too thin—or if you’ve got room to safely take on a mortgage.


How High Is Too High?


Most lenders follow maximum thresholds, especially for insured (high-ratio) mortgages.

As of now, those limits are typically:

GDS: Max 39%

TDS: Max 44%


Go above those numbers and your application could be declined, regardless of how confident you feel about your ability to manage the payments.


Real-World Example

Let’s say you’re earning $90,000 a year, or $7,500 a month.

You find a home you love, and the monthly housing costs (mortgage payment, property tax, heat) total $1,700/month.


GDS = $1,700 ÷ $7,500 = 22.7%


You’re well under the 39% cap—so far, so good.


Now factor in your other monthly obligations:

  • Car loan: $300
  • Child support: $500
  • Credit card/line of credit payments: $700
    Total other debt = $1,500/month


Now add that to the $1,700 in housing costs:
TDS = $3,200 ÷ $7,500 = 42.7%


Uh oh. Even though your GDS looks great, your TDS is just over the 42% limit. That could put your mortgage approval at risk—even if you’re paying similar or higher rent now.


What Can You Do?

In cases like this, small adjustments can make a big difference:

  • Consolidate or restructure your debts to lower monthly payments
  • Reallocate part of your down payment to reduce high-interest debt
  • Add a co-applicant to increase qualifying income
  • Wait and build savings or credit strength before applying


This is where working with an experienced mortgage professional pays off. We can look at your entire financial picture and help you make strategic moves to qualify confidently.


Don’t Leave It to Chance

Everyone’s situation is different, and debt service ratios aren’t something you want to guess at. The earlier you start the conversation, the more time you’ll have to improve your numbers and boost your chances of approval.


If you're wondering how much home you can afford—or want help analyzing your own GDS and TDS—let’s connect. I’d be happy to walk through your numbers and help you build a solid mortgage strategy.


Debra Sluz

Canadian Mortgage Expert

Smart Steps to Get Your Home Market-Ready

By Debra Sluz (Formerly Parker) • May 12, 2026
Thinking About Selling Your Home? Start With These 3 Key Questions Selling your home is a major move—emotionally, financially, and logistically. Whether you're upsizing, downsizing, relocating, or just ready for a change, there are a few essential questions you should have answers to before you list that "For Sale" sign. 1. How Will I Get My Home Sale-Ready? Before your property hits the market, you’ll want to make sure it puts its best foot forward. That starts with understanding its current market value—and ends with a plan to maximize its appeal. A real estate professional can walk you through what similar homes in your area have sold for and help tailor a prep plan that aligns with current market conditions. Here are some things you might want to consider: Decluttering and removing personal items Minor touch-ups or repairs Fresh paint inside (and maybe outside too) Updated lighting or fixtures Professional staging Landscaping or exterior cleanup High-quality photos and possibly a virtual tour These aren’t must-dos, but smart investments here can often translate to a higher sale price and faster sale. 2. What Will It Actually Cost to Sell? It’s easy to look at the selling price and subtract your mortgage balance—but the real math is more nuanced. Here's a breakdown of the typical costs involved in selling a home: Real estate agent commissions (plus GST/HST) Legal fees Mortgage discharge fees (and possibly a penalty) Utility and property tax adjustments Moving expenses and/or storage costs That mortgage penalty can be especially tricky—it can sometimes be thousands of dollars, depending on your lender and how much time is left in your term. Not sure what it might cost you? I can help you estimate it. 3. What’s My Plan After the Sale? Knowing your next step is just as important as selling your current home. If you're buying again, don’t assume you’ll automatically qualify for a new mortgage just because you’ve had one before. Lending rules change, and so might your financial situation. Before you sell, talk to a mortgage professional to find out what you’re pre-approved for and what options are available. If you're planning to rent or relocate temporarily, think about timelines, storage, and transition costs. Clarity and preparation go a long way. The best way to reduce stress and make confident decisions is to work with professionals you trust—and ask all the questions you need. If you’re thinking about selling and want help mapping out your next steps, I’d be happy to chat anytime. Let’s make a smart plan, together.

Bank of Canada Holds Rate at 2.25% — April 29, 2026

By Debra Sluz (Formerly Parker) • April 29, 2026
The Bank of Canada announced today that it is holding its target for the overnight rate at 2.25%, with the Bank Rate at 2.5% and the deposit rate at 2.20%. This decision comes against a backdrop of significant global uncertainty — and for Canadian homeowners, buyers, and anyone with a mortgage coming up for renewal, here's what it means.