Mortgage Approval 101: GDS & TDS Explained

Carla Sturm • September 3, 2025

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.


Carla Sturm
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Bank of Canada Holds Rate at 2.25% — September 2, 2026

By Carla Sturm • September 2, 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%. While Canada's economic recovery is broadening, a new layer of uncertainty has entered the picture. Here is what happened and what it means for your mortgage.

Monthly vs. Biweekly Mortgage Payments: Which Is Better?

By Carla Sturm • August 26, 2026
How Mortgage Payment Frequency Affects What You Pay Over Time You’ve probably heard the saying that there are two certainties in life: death and taxes. When it comes to your mortgage, there’s really just one certainty—you’ll repay what you borrow, plus interest. What is flexible, though, is how often you make your mortgage payments. And that choice can have a meaningful impact on how quickly you pay down your mortgage and how much interest you pay over time. The Six Mortgage Payment Frequencies Most lenders offer the following payment options: Monthly – 12 payments per year Semi-monthly – 24 payments per year Bi-weekly – 26 payments per year Weekly – 52 payments per year Accelerated bi-weekly – 26 payments per year Accelerated weekly – 52 payments per year Standard Payment Frequencies The first four options are designed to align with how you get paid. For example: Paid monthly? Monthly mortgage payments may make sense. Paid every two weeks? Bi-weekly payments can align nicely with your cash flow. With these standard options, regardless of how often you pay, the total amount paid over the year is the same —it’s simply divided into more frequent payments. What Makes “Accelerated” Payments Different Accelerated payments work differently—and this is where the real savings happen. With accelerated bi-weekly or accelerated weekly payments, you’re paying a slightly higher amount each time. That extra money goes directly toward reducing your mortgage principal, which lowers the interest you’ll pay over the life of the mortgage. A Simple Example Let’s assume a $1,000 monthly mortgage payment: Monthly: $1,000 once per month = $12,000 per year Semi-monthly: $500 twice per month = $12,000 per year Bi-weekly: $1,000 × 12 ÷ 26 = $461.54 every two weeks = $12,000 per year Accelerated bi-weekly: $1,000 ÷ 2 = $500 every two weeks = $13,000 per year With accelerated bi-weekly payments, you effectively make two extra payments per year without having to think about it. Those extra payments reduce your principal faster, which lowers interest costs over time. Accelerated weekly payments work the same way—you just make smaller payments more frequently. Why This Matters Long Term While it’s difficult to calculate exact savings due to variables like interest rates, terms, and amortization changes, maintaining an accelerated payment schedule over the life of your mortgage can reduce your amortization by up to three years and save a significant amount of interest. The Bottom Line Accelerated payments are a simple, automatic way to lower your overall cost of borrowing—without needing to make lump-sum payments or drastically change your budget. If you’d like to see how different payment frequencies would impact your mortgage specifically, feel free to reach out anytime. I’d be happy to walk through the numbers with you and help you choose the option that fits your goals.