The client
A rotational oilfield worker in Fort McMurray earns a stable T4 salary from his employer, paid biweekly regardless of which rotation he is on. On the side, he runs a small, unincorporated equipment-rental business — renting out a couple of trailers and a truck to other contractors between his own shifts. Because that side income is unincorporated self-employment income, it has to be handled under different rules than his T4 salary, even though it makes up a minority of his total earnings.
Borrower
Rotational oilfield employee
T4 salary + unincorporated side business
T4 salary
$9,800/month
Side business, year 1 net income
$22,400
T2125, line 135
Side business, year 2 net income
$31,600
T2125, line 135
Purchase price
$475,000, Fort McMurray
Down payment
$47,500 — 10%
Under 20%, so the file is default-insured
The problem
A T4 income at face value would normally need nothing more than paystubs and an employment letter. The moment a self-employed side business enters the picture, though, that portion of income is subject to the same two-year-averaging discipline that applies to any unincorporated sole proprietorship — regardless of how small it is relative to the T4 salary. Treating the side income as a simple annualization of the most recent, stronger year would overstate it; ignoring it entirely would understate the client's real qualifying power.
There was a second wrinkle: the side business had financed a truck loan against its own equipment, serviced from business revenue rather than personal income. Whether that debt belongs in the personal TDS calculation or can be excluded as a business obligation is a lender-by-lender decision, not a fixed rule — and getting it wrong in either direction changes the ratio meaningfully.
The file needed both income streams correctly averaged and combined, and a clear, documented case for how the equipment loan should be treated. Combined files like this are becoming more common as the average new mortgage amount climbs and a single T4 income increasingly isn't enough on its own to clear it comfortably.
There is a version of this file that goes wrong purely on the paperwork, not the math: a lender's checklist sees "self-employed" and asks for a full package of corporate documents that simply do not exist for an unincorporated sideline run out of a personal bank account. Explaining upfront that the side business has no separate legal entity, no shareholders, and no financial statements beyond the T2125 itself — and that this is exactly what the sole-proprietorship rules anticipate, not a gap in the file — heads off a documentation request that would otherwise stall the T4 side of the file too.
The numbers
The T4 salary needs no averaging; the side business does — and the two streams simply add together once each is correctly calculated.
| Combining T4 and averaged side-business income | Amount |
|---|---|
| Side business net income, year 1 (T2125, line 135) | $22,400 |
| Side business net income, year 2 (T2125, line 135) | $31,600 |
| Two-year total | $54,000 |
| Two-year average, annual | $27,000 |
| Side business income, expressed monthly | $2,250 |
| T4 salary, monthly | $9,800 |
| Total qualifying income | $12,050 |
At 10% down on $475,000, the loan sits at exactly 90% LTV — the top of the 85.01–90% CMHC premium band.
| Structuring the insured loan | Figure |
|---|---|
| Purchase price | $475,000 |
| Down payment (10%) | −$47,500 |
| Base mortgage | $427,500 |
| CMHC premium — 3.10% at 85.01–90% LTV | +$13,252 |
| Total insured mortgage | $440,752 |
| GDS / TDS at the qualifying rate (7.89%) | Result |
|---|---|
| Payment $3,333 + tax $340 + heat $150, ÷ income $12,050 | GDS 31.7% |
| Add the $180/mo personal credit-card payment, ÷ income $12,050 | TDS 33.2% ✓ |
The side business's own equipment loan — $540/month, serviced directly from business revenue — was deliberately excluded from this TDS calculation. The lender accepted the exclusion on the strength of twelve months of business bank statements showing the payment consistently coming from business, not personal, funds.
The solution
A RECA-licensed Alberta mortgage associate did two things to combine the income correctly and protect the ratio.
First, applied two-year averaging to the side business only, leaving the T4 salary untouched. The two-year averaging approach that governs unincorporated self-employment income applied cleanly to the trailer-rental sideline's net income, while the T4 salary was verified the ordinary way — paystubs, an employment letter, and a NOA, following the same line-by-line method our guide to calculating self-employed income from a T1 and T2 sets out.
Second, built a documented case for excluding the equipment loan from personal TDS. Not every lender will agree to exclude a business-serviced debt, so the associate confirmed the target lender's policy and requirements — a full year of business bank statements showing the payment source — before submitting, rather than hoping the underwriter would agree at conditions. Getting that confirmation in writing before submission, rather than arguing for it after a conditional approval already assumed the debt was included, was what actually protected the ratio.
The outcome
Approved and funded insured at 90% LTV, 25-year amortization, with both income streams combined at $12,050/month and the side business's own equipment loan excluded from the personal debt-service calculation on documented business-payment evidence.
Alberta has no provincial land transfer tax; closing costs were confirmed directly with the lender's solicitor and kept as a category rather than an estimated dollar figure.
What to take from this file
- 01Any unincorporated self-employment income triggers two-year averaging for that portion of the file — even when it is a minority share of total income sitting alongside a stable T4 salary.
- 02T4 income does not need averaging just because a side business shares the file. Verify each income stream by its own correct method rather than applying one rule to both.
- 03A business-serviced debt can sometimes be excluded from personal TDS — but only with documented proof of the payment source, and only if the specific lender's policy allows it.
- 04Confirm a lender's exclusion policy before submitting, not at conditions. Finding out mid-file that a lender won't exclude a debt can blow a ratio that was budgeted to pass.
Sources
Every regulatory figure in this file traces to one of these primary sources. Client details and anything that varies by lender are illustrative, as flagged below.
- ▸CMHC — Purchase (Mortgage Loan Insurance) — default-insurance premium schedule by LTV band (25-year amortization).
- ▸CMHC — CMHC Home Start — minimum down payment tiers (5%/10%) and the $1.5M insured price cap.
- ▸OSFI — Minimum qualifying rate for uninsured mortgages — the minimum qualifying rate — greater of contract rate + 2% or 5.25%.
- ▸CMHC — CMHC Reviews Underwriting Criteria — GDS 39% / TDS 44% maximums and the 600 credit-score floor for insured files.
- ▸Provincial/territorial mortgage-broker legislation fetched directly (bclaws.gov.bc.ca, legisquebec.gouv.qc.ca, fcaa.gov.sk.ca, web2.gov.mb.ca, nslegislature.ca, assembly.nl.ca) plus FCNB's own site for NB and CanLII's index for PE — see notes for per-province method — provincial mortgage regulators and licence titles.
Illustrative in this file — lender-specific, not rules:
- ▸5.89% contract rate — rates move daily; not a quote.
- ▸$340/mo tax and $150/mo heat estimate — lender-standard estimates, not rules.
- ▸Excluding the equipment loan from TDS because it is serviced from business revenue — each lender decides for itself whether a business-serviced debt can be excluded, and on what proof.
Authority & provenance
How this case file was built
We publish the origin, the verification method and the reviewer for every case file, so you can judge how far to trust it before you rely on it with a client.
Where it comes from
Derived from files handled by Treadstone’s fulfillment desk and from scenarios contributed by partner brokerages. Names, employers, exact amounts and dates are changed so no client or file is identifiable.
Provenance: Composite — a pattern seen repeatedly on fulfilled files, not a single transaction.
What is verified
Every regulatory figure traces to a primary source listed above and was checked against it on the date shown. The arithmetic is recomputed by machine on every rebuild.
Anything that varies by lender is labelled illustrative rather than stated as a rule.
Who reviewed it
Reviewed for Canadian regulatory accuracy before publication, and re-checked whenever a cited rule changes.
Reviewed by: Nicholas Parson, Treadstone Associates — reviews every case file before publication.
This case file is professional reference material for licensed mortgage professionals. It is not advice to a borrower, and it is not a lender commitment. Insurer rules, qualifying rates and provincial taxes change — confirm the current position with the insurer, regulator or lender before you rely on any figure here in a live file.