The client
Rather than buy out her spouse's share of their Cornwall matrimonial home, one spouse in this separation is selling out of it and buying a smaller home instead. Her existing $240,000 mortgage carries a legacy 2.89% rate with 24 months still left in its term — low enough that everyone involved assumed it would simply have to end the day the matrimonial home's sale closed.
Existing mortgage balance
$240,000
Legacy rate, 24 months left in the term
New purchase price
$305,000
A smaller Cornwall home
Down payment
$65,000
From her share of the sale proceeds
Remaining amortization
18 years
Keeping spouse's income
$7,300/month
Alone, post-separation
The problem
Selling out of a matrimonial home usually means the existing mortgage on it is paid out and discharged in full — and the natural assumption is that whatever rate that mortgage carried disappears with it. That assumption is usually right when the seller isn't buying again right away. It is not automatically right when they are.
What porting actually preserves
- ▸A lender's portability feature lets an existing mortgage's rate and remaining amortization carry across to a new property, rather than ending with the old one
- ▸The new purchase has to close inside that lender's port window, timed around the old mortgage's discharge date — not simply at some point before the term matures
- ▸Missing that window turns the file into an ordinary fresh mortgage at whatever rate is available that day, with none of the old rate preserved
Neither spouse had any reason to know porting was even available — the separation agreement dealt with dividing the sale proceeds, not with what happened to the mortgage rate attached to the property being sold.
The numbers
Two comparisons decide what porting is actually worth here: the payment itself, and the rate the new mortgage has to qualify at.
| Porting the legacy rate versus a fresh mortgage | Amount |
|---|---|
| Payment ported at 2.89%, 18 years remaining | $1,424/mo |
| Payment on a fresh mortgage at 4.99%, same balance and amortization | $1,679/mo |
| Monthly difference | $255 |
| Value of porting over the term left | Figure |
|---|---|
| Monthly difference × 24 months left in the term | $6,120 |
| Prepayment penalty avoided by porting instead of breaking | $7,200 |
| Combined value of porting | $13,320 |
That $13,320 is what was actually riding on the two closings — the matrimonial home's sale and the new purchase — landing inside the lender's port window and avoiding a prepayment penalty entirely.
The qualifying rate moves too, not just the payment
| Qualifying at the minimum qualifying rate | Ported | Fresh |
|---|---|---|
| Minimum qualifying rate | 5.25% | 6.99% |
| Qualifying payment, 18 years | $1,712/mo | $1,942/mo |
| Total debt service on the qualifying payment | 31.5% | 34.6% |
Porting's 2.89% contract rate qualifies at OSFI's minimum qualifying rate floor of 5.25%, since 2.89% plus 2 points doesn't reach it. A fresh mortgage at 4.99% qualifies nearly two full points higher, at 6.99% — both files clear comfortably on this income, but a tighter file could have failed on the fresh-mortgage number alone. This is exactly the gap new-vs-outstanding mortgage rates in Canada have opened up since 2022, and exactly what porting is designed to protect against.
The solution
A mortgage agent licensed under Ontario's Mortgage Brokerages, Lenders and Administrators Act treated the mortgage's portability as the starting option, not an afterthought raised only once a fresh-mortgage quote came back worse.
First, confirmed the existing lender's port window and exactly what discharge date it ran from, rather than assuming any closing date before the term's maturity would qualify.
Second, coordinated the matrimonial home's sale closing with the new purchase's closing so both fell inside that window, flagging early that a delay on the buyer's side of the sale would put the port at risk.
Third, sized the new purchase's down payment to her $65,000 share of the sale proceeds, keeping the ported balance unchanged at $240,000 so no blended rate was needed at all.
The outcome
The purchase closed on the ported $240,000 balance at 2.89%, qualifying at 5.25% with total debt service of 31.5% on the keeping spouse's income alone — against the 6.99% qualifying rate and 34.6% result a fresh mortgage at that day's rates would have produced.
Both qualifying-rate figures are informational for this file, since 31.5% and 34.6% both clear comfortably under any lender's ratio maximums — the point is how much closer to the edge a fresh mortgage would have sat, not that porting was the only way to qualify at all.
What to take from this file
- 01A mortgage's rate does not automatically die with the property it's registered against. Porting can carry it — and the remaining amortization — to a new purchase instead.
- 02Porting only works inside the lender's own window around the old mortgage's discharge date. Coordinate both closings to that window before assuming the rate is safe.
- 03The minimum qualifying rate moves with the contract rate, not just the payment does. A low legacy rate can mean qualifying at the 5.25% floor instead of two points above a much higher fresh rate.
- 04A missed port window doesn't just cost a penalty. It can also raise the qualifying rate enough to change whether a tighter file clears the ratios at all.
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.
- ▸OSFI — Minimum qualifying rate for uninsured mortgages — the minimum qualifying rate — greater of contract rate + 2% or 5.25%.
- ▸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:
- ▸2.89% legacy rate / 4.99% fresh-mortgage rate — rates move daily; neither is a quote.
- ▸the $7,200 penalty and the port-window terms — IRD penalties and portability windows are set by each lender's own policy, not a universal rule.
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.