Porting a Mortgage: How It Works, What It Costs, and When It Is Worth It

Buyer Advice Dave Dubbin August 25, 2026

Porting a mortgage means taking your existing mortgage, with its rate and its remaining term, and moving it to the home you are buying instead of paying it out and starting over. Whether it is worth doing comes down to one comparison: is your current rate lower than what you could get today? If yes, porting protects something valuable and you should fight to keep it. If no, you may be paying a penalty to keep a rate you would not choose, and breaking can be the cheaper move. Everything else is detail.

Thinking about a move and not sure what your current mortgage is worth to you? Start with what your place is worth today, then we can work backwards to the financing.

What porting actually is

Your mortgage is a contract between you and a lender, secured against a specific property. Sell that property and the contract normally ends, which triggers a prepayment penalty. Porting is the lender agreeing to release the old security and attach the same contract to a new one, so the rate and the maturity date carry over.

Holding house keys in front of an entrance

Photo: Unsplash

Two things about porting surprise people. The first is that it is not automatic. Full feature mortgages usually allow it. Cheaper restricted mortgages, the ones with the eye catching rate, often limit or prohibit it. That is the trade you made when you signed. The second is that porting is an approval, not a transfer. The lender underwrites the new property and re-underwrites you.

The question that decides everything

A mortgage at a below market rate is an asset. It is a contract obligating someone to lend you money more cheaply than they would today, and letting it lapse throws that value away. A mortgage at an above market rate is the opposite, and porting it is like renewing a bad phone plan because cancelling has a fee.

So start by finding out what today looks like. Here is where five year fixed rates sat in Canada as of August 21, 2026, per Ratehub.

Best available (Big 6 / Simplii)

4.09%

Scotiabank

4.29%

TD Bank

4.49%

Bank of Montreal

4.51%

CIBC

4.59%

RBC Royal Bank

4.89%

Five year fixed rates as advertised on Ratehub, August 21, 2026. Bars scaled to 5.20 per cent. The lowest insured five year fixed on that date was 3.94 per cent and the lowest five year variable was 3.35 per cent. The Bank of Canada held its policy rate at 2.25 per cent on July 15, 2026, with prime at 4.45 per cent. The next decision is September 2, 2026.

If your rate starts with a three, you are almost certainly better off porting. If it starts with a five, run the numbers before you assume anything.

Port and increase, and how the blend is calculated

Most people moving are buying something pricier, so they need more money than the old mortgage carried. That is a port and increase, sometimes called a blend and extend. The lender keeps your old balance at your old rate, prices the new money at a current rate, and charges you the weighted average of the two.

Worked example. You owe $400,000 at 3.49 per cent with 30 months left on the term. The new place needs a $600,000 mortgage, so you are adding $200,000 of new money at 4.29 per cent.

Existing balance at 3.49 per cent	$400,000
New money at 4.29 per cent	$200,000
Blended rate on $600,000	3.76%

The math is just each piece weighted by its share: 400,000 times 3.49 per cent plus 200,000 times 4.29 per cent, all divided by 600,000. Now compare that to breaking the old mortgage and taking a fresh $600,000 at the best available 4.09 per cent.

First year cost	Port and blend	Break and re-borrow
Rate	3.76%	4.09%
Interest on $600,000	$22,540	$24,540
Prepayment penalty (three months interest)	$0	$3,490
Year one total	$22,540	$28,030

Illustrative, using simple interest on the opening balance to keep the comparison readable. Your actual amortization schedule will differ. Rates as advertised on Ratehub, August 21, 2026.

About $5,500 in year one, and the advantage keeps compounding for the remaining 30 months. That is the whole case for porting in one table.

Three related pieces if you are working through a move:

The timing window nobody mentions until it is a problem

Porting is not a permanent right. Lenders give you a window between the sale closing and the purchase closing, and if you miss it, the port dies and the penalty lands. The window varies by lender. Some are tight, some are generous, and none of them will tell you unless you ask. Get yours in writing before you sign anything with a closing date attached.

Same day closings are the cleanest. If your sale closes before your purchase, you may be able to bridge the gap with short term financing, which is a separate product with its own cost. If your purchase closes first, some lenders will let you port forward. Some will not. This is the single most common place a port goes sideways, and it is entirely avoidable with one phone call early.

You still have to qualify

People assume that because they already have the mortgage, the approval carries over. It does not. The lender underwrites the new property and re-checks your income, your debts and your credit. If you changed jobs, went self employed, took on a car loan, or bought a place the lender does not like, the port can be refused.

The stress test applies too. Under the federal minimum qualifying rate, unchanged as of January 29, 2026, you have to qualify at the greater of 5.25 per cent or your contract rate plus two per cent. With the best five year fixed at 4.09 per cent, that means qualifying around 6.09 per cent even though you would pay 4.09. The gap between what you pay and what you must prove you could pay is the whole point of the rule, and it is what decides your maximum purchase price.

When porting is not the right answer

If your rate is above today market, the calculation flips and the answer gets close. Say you owe $400,000 at 5.29 per cent with 30 months left. On a fixed mortgage the penalty is the greater of three months interest or the interest rate differential, and with a contract rate well above current pricing the differential is the one that bites. Three months interest would be about $5,290. The differential could be roughly double that, depending entirely on which comparison rate your lender uses, and lenders calculate this very differently. Moving that balance to 4.09 per cent would save on the order of $12,000 in interest over the remaining term. Close enough that the lender specific method decides it.

Two other cases where porting loses. If you are downsizing and the new mortgage is smaller, you may face a partial prepayment penalty on the difference anyway. And if the port forces you to stay with a lender whose renewal offers are uncompetitive, you have bought a short term saving and a long term problem.

What would change this thesis

Rate direction, mostly. Fixed rates in Canada are priced off Government of Canada bond yields rather than the Bank of Canada policy rate, and yields have been firm through the summer with July inflation at 3.0 per cent. If yields fall and five year fixed pricing drops back through the mid threes, a lot of existing mortgages stop being assets and porting stops being obviously right. If yields rise instead, protecting a low rate becomes more valuable, not less. Either way, the decision is arithmetic, and the arithmetic changes every time the market does.

One more thing worth saying plainly: we are real estate brokers, not mortgage brokers. The numbers above are meant to show you how the comparison works, not to substitute for a quote from your lender.

If you are planning a move and you have a rate worth protecting, the port question should be settled before you list, not after you have an accepted offer. Book a call and we will map the closing dates against your lender window and tell you where the pressure points are. If your rate is not worth protecting, we will tell you that too.

Dave Dubbin
Real Estate Expert
Dave Dubbin & Associates
Real Estate Broker for Etobicoke and Toronto Sotheby's International Realty, Canada