Key Takeaways
- 1.At a 4.59% contract rate, the stress test qualifying rate is 6.59% (contract + 2%), well above the 5.25% floor. Every dollar of your qualification is measured against this higher rate.
- 2.With $60K down (8%) on a $750K home, the couple's GDS ratio is approximately 35.4% — under the 39% ceiling. They pass the housing-cost test.
- 3.Add the $450/month car payment and the TDS ratio climbs to approximately 38.8% — under the 44% ceiling but noticeably tighter. A second car payment or student loan could push them over.
- 4.The break-even income to clear both GDS (39%) and TDS (44%) on this purchase with the car payment is approximately $145,000. The couple's $160K income provides a $15K buffer.
- 5.Putting 20% down ($150K) instead of 8% eliminates CMHC insurance, drops the mortgage by $66K, and reduces the GDS ratio to roughly 29.5% — but requires $90K more in savings.
The Stress Test Rate: How It's Calculated
OSFI's B-20 guideline requires federally regulated lenders to qualify borrowers at the higher of the contractual mortgage rate plus 2%, or a floor rate of 5.25%. In early 2025, typical 5-year fixed rates sit around 4.49–4.69%. Adding 2% gives a qualifying rate of 6.49–6.69%, which exceeds the 5.25% floor — so the contract-plus-2% formula governs.
Stress test rate calculation:
Contract rate (5-year fixed): 4.59%
Stress test rate: max(4.59% + 2.00%, 5.25%)
= max(6.59%, 5.25%)
= 6.59%
This is the rate used to calculate your qualifying mortgage payment — not the rate you actually pay.
Your actual monthly payment will be based on 4.59%, but OSFI wants to know: can you still make the payments if rates climb to 6.59%? Every ratio in this article uses the stress test rate for the mortgage payment calculation.
Base Scenario: $60K Down on a $750K Home
The couple puts $60K down on a $750K purchase. That is 8% of the purchase price, which means the mortgage requires CMHC default insurance. The insurance premium adds directly to the mortgage balance.
Mortgage structure:
Purchase price: $750,000
Down payment: $60,000 (8.0%)
Mortgage before insurance: $690,000
CMHC insurance premium:
Down payment 5–9.99%: 4.00% premium on mortgage amount
Premium: $690,000 × 4.00% = $27,600
Total insured mortgage: $690,000 + $27,600 = $717,600
Monthly payment at stress test rate (6.59%, 25-year amortization):
Monthly payment: $4,854
(Actual payment at 4.59% contract rate: $4,013/month —
you pay this, but qualify at the higher amount)
The $27,600 CMHC premium is significant — it adds roughly $187/month to the stress-test payment. This is the cost of putting less than 20% down, and it directly tightens the GDS/TDS math. For context on how Alberta's tax environment affects this couple's take-home pay, see our Alberta vs. Ontario income tax comparison.
GDS Ratio: The Housing-Cost Test
The Gross Debt Service ratio measures total housing costs against gross income. It must not exceed 39% at most lenders.
GDS calculation (monthly):
Mortgage payment (at 6.59%): $4,854
Property taxes: $375/month (~$4,500/year for a $750K Alberta home)
Heating costs: $150/month (lender standard estimate)
Condo fees: $0 (assuming detached home)
Total housing costs: $4,854 + $375 + $150 = $5,379/month
Gross monthly income: $160,000 ÷ 12 = $13,333
GDS = $5,379 ÷ $13,333 = 40.3%
GDS ceiling: 39%
Result: FAIL — over by 1.3 percentage points
This is tighter than it first appears. The CMHC insurance premium inflates the mortgage balance by $27,600, which pushes the stress-test payment high enough to breach the 39% GDS ceiling. Some lenders and insurers allow GDS up to 39% with strong credit (beacon 680+) and may stretch to the “exception” threshold of approximately 39% with compensating factors. The couple is right at the boundary — a slightly lower purchase price or slightly higher income tips them back under.
TDS Ratio: Adding the Car Payment
The Total Debt Service ratio layers all non-housing debt on top of housing costs. The ceiling is 44%. This is where the couple's $450/month car payment enters the equation.
TDS calculation (monthly):
Total housing costs (from GDS): $5,379
Car payment: $450
Other debts: $0
Total debt service: $5,379 + $450 = $5,829/month
Gross monthly income: $13,333
TDS = $5,829 ÷ $13,333 = 43.7%
TDS ceiling: 44%
Result: PASS — but only 0.3 percentage points of room
The TDS technically passes, but the GDS fails at 40.3%. Both ratios must pass simultaneously. Even a small additional monthly obligation — a $200 student loan payment, a credit card minimum — would push TDS over 44% as well. The car payment alone is not the problem; the real squeeze comes from the CMHC-inflated mortgage at the stress test rate.
Break-Even Income: What You Actually Need
Working backward from the ratio ceilings, here is the minimum gross household income needed to qualify for this exact mortgage with and without the car payment.
Break-even income for GDS ≤ 39%:
Required: $5,379/month ÷ 0.39 = $13,792/month
Annual: $13,792 × 12 = $165,500
Break-even income for TDS ≤ 44% (with $450 car payment):
Required: $5,829/month ÷ 0.44 = $13,248/month
Annual: $13,248 × 12 = $159,000
Binding constraint: GDS at $165,500
The couple needs approximately $165,500 in gross income to clear both thresholds. At $160,000, they are $5,500 short on the GDS side.
Without the car payment:
GDS is unchanged at $165,500 (car payment does not affect GDS)
TDS break-even drops to: $5,379 ÷ 0.44 = $12,225/month = $146,700
The binding constraint remains GDS.
An important insight: eliminating the car payment does not fix the GDS problem. The car payment only affects TDS. To pass GDS at $160K income, the couple needs to either reduce the purchase price, increase the down payment above 20% (eliminating CMHC insurance), or find a lender willing to stretch the GDS ceiling. For self-employed Alberta buyers dealing with income verification complexities, see our CRA instalment calculator for Alberta self-employed contractors.
Side-by-Side: 10% Down vs. 20% Down
The down payment size dramatically changes the stress test math because it determines whether CMHC insurance applies and how large the mortgage balance is. Here is a direct comparison.
| Metric | 8% Down ($60K) | 10% Down ($75K) | 20% Down ($150K) |
|---|---|---|---|
| Mortgage before insurance | $690,000 | $675,000 | $600,000 |
| CMHC premium rate | 4.00% | 3.10% | None |
| CMHC premium | $27,600 | $20,925 | $0 |
| Total mortgage | $717,600 | $695,925 | $600,000 |
| Stress test payment | $4,854/mo | $4,707/mo | $4,059/mo |
| GDS ratio | 40.3% | 39.2% | 34.4% |
| TDS ratio (with car) | 43.7% | 42.6% | 37.8% |
| Qualification result | FAIL (GDS) | BORDERLINE | PASS |
All payments calculated at 6.59% stress test rate, 25-year amortization. Property taxes $375/month, heating $150/month. Car payment $450/month included in TDS only.
The 20% down scenario is the cleanest pass — GDS at 34.4% and TDS at 37.8% leave comfortable room. But it requires an additional $90K in savings. For an Alberta couple, that might mean tapping the Home Buyers' Plan via RRSP or an FHSA for first-time buyers to assemble the larger down payment with tax advantages.
What If They Pay Off the Car First?
Eliminating the $450/month car payment before applying does not affect GDS (which only counts housing costs), but it does improve TDS and frees up cash flow that lenders consider indirectly.
Without car payment ($60K down scenario):
GDS: 40.3% — unchanged (still fails at 39% ceiling)
TDS: $5,379 ÷ $13,333 = 40.3% — passes (under 44%)
Without car payment ($75K / 10% down scenario):
GDS: 39.2% — unchanged (borderline)
TDS: $5,232 ÷ $13,333 = 39.2% — comfortably passes
The car payment is not the binding constraint.
GDS is the problem. To fix GDS, the couple needs to either:
1. Increase income to ~$165,500 (GDS break-even)
2. Increase down payment to 20% ($150K) to eliminate CMHC
3. Lower purchase price to ~$710K (with $60K down)
4. Find a lender allowing GDS exception above 39%
The CMHC Insurance Effect
CMHC mortgage default insurance is required when the down payment is less than 20%. The premium is a percentage of the mortgage amount that gets added to the balance — inflating every payment and every ratio calculation.
CMHC premium schedule (2025):
Down payment 5.00–9.99%: 4.00% premium
Down payment 10.00–14.99%: 3.10% premium
Down payment 15.00–19.99%: 2.80% premium
Down payment 20.00%+: no insurance required
Impact on this purchase:
At 8% down: $690K × 4.00% = $27,600 premium
At 10% down: $675K × 3.10% = $20,925 premium
At 15% down: $637.5K × 2.80% = $17,850 premium
At 20% down: $0 premium
The jump from 8% to 10% down saves $6,675 in insurance.
The jump from 10% to 20% saves $20,925 and changes the entire qualification picture.
For many Alberta couples in this income range, the strategic decision is whether to stretch for 20% down or accept the insurance cost and buy sooner. The math favours 20% when you can realistically save the difference within 12–18 months — beyond that, rising home prices may offset the insurance savings.
Alberta-Specific Advantages
Alberta buyers have several structural advantages that make the $750K purchase more achievable than it would be in BC or Ontario.
No provincial land transfer tax:
Alberta: ~$350 title transfer fee
BC (on $750K): ~$13,000 property transfer tax
Ontario (on $750K): ~$12,475 land transfer tax
Toronto (on $750K): ~$24,950 (municipal + provincial)
Savings vs. BC/Ontario: $12,000–$24,000
Lower property taxes:
Alberta average effective rate: ~0.60–0.80% of assessed value
$750K home: ~$4,500–$6,000/year
Used in our calculation: $4,500/year ($375/month)
No provincial sales tax:
Alberta has no PST (only 5% GST applies)
This does not directly affect the mortgage but reduces
the overall cost of furnishing and maintaining the home.
The land transfer tax savings alone could be redirected to the down payment. An Alberta couple saving $12,000+ on closing costs effectively gets a head start on the 20% down payment threshold. For couples also weighing how Alberta's income tax advantage affects their overall financial plan, see our Alberta vs. Ontario income tax calculator.
Practical Options for This Couple
The couple earns $160K and has $60K saved. They fail GDS at 40.3% on a $750K home. Here are the realistic paths forward, ranked by feasibility.
Option 1: Lower the purchase price to ~$710K
Mortgage before insurance: $650K
CMHC premium (4.00%): $26,000
Total mortgage: $676,000
Stress test payment: $4,573/month
GDS: ($4,573 + $360 + $150) ÷ $13,333 = 38.1% — PASS
TDS (with car): ($5,083 + $450) ÷ $13,333 = 41.5% — PASS
Option 2: Save to 20% down ($150K)
Need to save: $90K more
At $2,000/month savings: ~45 months (3.75 years)
At $3,000/month savings: ~30 months (2.5 years)
GDS at 20% down: 34.4% — comfortable PASS
Option 3: Wait for a raise to ~$166K
Need: ~$5,500 more gross income ($2,750 per person)
GDS at $166K: ($5,379 ÷ $13,833) = 38.9% — PASS
TDS at $166K: ($5,829 ÷ $13,833) = 42.1% — PASS
Option 4: Use a credit union (non-OSFI lender)
Some credit unions are provincially regulated and not subject
to the federal stress test. Rates may be higher, and you lose
the portability of a federally regulated mortgage. This is a
viable option but compare total cost of borrowing carefully.
Actual Monthly Costs vs. Stress Test Costs
The stress test is a qualification tool, not a payment schedule. Here is what the couple actually pays each month if they qualify (at the contract rate of 4.59%).
| Cost | Stress Test (6.59%) | Actual (4.59%) |
|---|---|---|
| Mortgage payment | $4,854 | $4,013 |
| Property taxes | $375 | $375 |
| Heating | $150 | $150 |
| Car payment | $450 | $450 |
| Total monthly obligations | $5,829 | $4,988 |
| As % of gross income | 43.7% | 37.4% |
Based on $717,600 insured mortgage (8% down), 25-year amortization. Actual payment uses 4.59% contract rate.
At the actual contract rate, the couple's total monthly obligations consume 37.4% of gross income — well within what most financial planners consider manageable for a dual-income household with no children. The stress test adds $841/month in phantom costs that exist only for qualification purposes. For families juggling home-buying savings with RRSP decisions, our FHSA vs. RRSP Home Buyers' Plan comparison breaks down which account saves more tax on the way in.
Important Disclaimer
This article provides general information about the OSFI mortgage stress test, GDS/TDS ratio calculations, and CMHC insurance premiums as of 2025. Mortgage rates, CMHC premium schedules, OSFI qualifying rate floors, and lender-specific GDS/TDS exception policies are subject to change. Property tax rates vary by municipality within Alberta. Individual lenders may apply additional qualification criteria including credit score minimums, employment verification, and asset requirements. This is not financial, legal, or mortgage advice. Consult a licensed mortgage broker or financial advisor for guidance specific to your situation.