Mortgage Approval 101: GDS & TDS Explained

Josh Perez • August 13, 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.


Josh Perez
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Deposit vs. Down Payment: Key Differences for Homebuyers

By Josh Perez • February 18, 2026
When you’re buying a home, two terms often cause confusion: deposit and down payment . While they’re related, they serve very different purposes in the homebuying process. Here’s what you need to know. What Is a Deposit? A deposit is the money you provide when you make an offer on a property. Think of it as a show of good faith that proves you’re serious about purchasing. How it works : Typically, you provide a certified cheque or bank draft that your real estate brokerage holds in trust. If your offer is accepted, the deposit remains in trust until the deal moves forward. If negotiations fall through, the deposit is refunded. Connection to your down payment : Once the sale is finalized, your deposit becomes part of your total down payment. Why it matters : The amount is negotiable, but a larger deposit can make your offer more attractive in a competitive market. Keep in mind, however, that if you back out after conditions are removed, you risk losing your deposit. What Is a Down Payment? Your down payment is the amount you contribute toward the purchase price of your home when securing a mortgage. Minimum requirement : In Canada, the minimum down payment is 5% of the home’s purchase price. Anything less than 20% requires mortgage default insurance. Sources : Down payments can come from your savings, the sale of another property, RRSP withdrawals (through the Home Buyers’ Plan), a gift from family, or even borrowed funds. Example: How They Work Together Imagine you’re buying a $400,000 home with a 10% down payment ($40,000). When you make your offer, you provide a $10,000 deposit . Once conditions are met, that deposit is transferred to your lawyer’s trust account. At closing, you add the remaining $30,000 to complete your full down payment. The lender provides the rest—$360,000—through your mortgage. The Bottom Line Your deposit shows commitment and secures your offer, while your down payment is what makes the mortgage possible. Together, they work hand in hand to get you into your new home. 📞 If you’d like clarity on deposits, down payments, or any other part of the mortgage process, let’s connect. I’d be happy to walk you through it step by step.
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Is a 5% Down Payment a Mistake? Here’s the Unpopular Truth.

By Josh Perez • February 15, 2026
Discover why a 5% down payment isn’t always irresponsible. Learn when a low down payment is a smart financial move for Ontario homebuyers and when it’s a risk.