Short answer: porting lets you transfer your existing mortgage, rate, remaining term, and balance, to a new property when you move, instead of breaking it and paying a prepayment penalty. It's a genuinely useful tool, but it isn't automatically the cheapest option, and not every mortgage is portable.
How Porting Actually Works
If your mortgage is portable (check your commitment or ask your lender, most fixed-rate mortgages are, most variable-rate mortgages are not), you can carry your existing rate and remaining term over to a new property, avoiding the prepayment penalty you'd otherwise owe for breaking the mortgage mid-term.
Blend and Increase
If your new home costs more than your old one, most lenders offer a "blend and increase," porting your existing balance and rate, then adding a top-up amount at today's rate, blended together into one new rate for the combined mortgage.
The Time Window Matters
Porting isn't open-ended. Lenders typically require the new purchase to close within a set window, often somewhere between 30 and 120 days of selling (or sometimes before selling) your current home, so timing your sale and purchase closely matters if you want to port.
You Still Have to Requalify
Porting doesn't skip underwriting. You'll still need to qualify for the mortgage on the new property, and any top-up portion is subject to the current stress test, even though your original ported balance isn't being re-stress-tested in the same way.
When Porting Doesn't Actually Save You Money
If current rates have dropped well below your existing rate, porting a higher rate forward, even blended, can cost more over time than simply breaking your mortgage, paying the penalty, and starting fresh at today's lower rate. The right answer depends on the size of the penalty versus the size of the rate gap, which is exactly the kind of comparison worth running before deciding either way.
Moving and Not Sure Whether to Port?
We'll compare porting against breaking and refinancing, real numbers, before you list your home. Talk to Sean first.