A rental offset that failed at one lender, and passed cleanly at another.

The borrower's existing rental condo carries a $1,900 monthly payment (principal, interest, taxes, and condo fees) and rents for $2,200. On its face, that's a property that more than covers itself — a $300 monthly surplus most borrowers would assume simply adds to their qualifying income.

Whether an underwriter treats that $300 surplus as straightforward good news depends entirely on the method the lender uses to bring rental income into the debt service ratio calculation — and that method is not the same across the market.

The first lender in this walkthrough — call it Lender A — used an offset method: rent is netted directly against the rental property's own carrying costs, and only a documented, discounted surplus (if any survives the discount) gets added to the borrower's income; if the offset leaves a shortfall instead, that shortfall is added as a debt rather than an income boost.

Under that method, once a standard discount was applied to the rental income before the offset, the property no longer fully covered its own carrying costs on paper — turning what looked like a $300 surplus into a modest shortfall counted against the borrower's ratios. Combined with the new purchase, the file's total debt service ratio broke Lender A's threshold.

A second lender in this walkthrough — Lender B — used a different, add-back-style method: a percentage of the property's gross rental income is added directly to the borrower's total income, with the property's own mortgage payment counted as a debt in the usual way, rather than netting the two against each other first.

Run through that method, the same lease and the same numbers produced a meaningfully more favourable ratio, and the file cleared without needing any change to the borrower's documentation, the rent, or the purchase itself. Nothing about the file changed between submissions — only the lens it was read through.

There is no single national standard governing exactly how a Canadian lender must credit rental income in a debt service ratio — it's one of the areas mortgage products and lender policies genuinely differ from one institution to the next, alongside things like amortization limits and prepayment terms. Both an offset approach and an add-back approach are legitimate, commonly used methods — they simply produce different results on the same file.

That's exactly why this isn't a case of one lender being wrong. It's a case of two defensible methods landing in different places, which is precisely why a broker who understands the difference can save a file that would otherwise look dead.

• →Before submitting a file with an existing rental property, run the numbers mentally under both an offset and an add-back method — the gap between the two can be the difference between an approval and a decline.
• →A single decline on ratio grounds doesn't mean the deal is dead — it may mean the method didn't suit the file, not that the borrower doesn't qualify anywhere.
• →Document the rental income thoroughly regardless of destination lender — lease, T776 if available, and proof of collection — since both methods still require the underlying paper trail.