That cheaper renewal offer may have quietly reset your amortization
A renewal quote with a lower payment often isn't a better rate — it's a longer amortization. On a $500,000 balance, going back to 25 years drops the payment $389 a month and leaves you owing $26,000 more at the end of the term.
You open the renewal letter, or the broker sends over three options, and one of them has a payment that's a few hundred dollars a month lower than the others. It looks like the better deal.
Check the amortization before you sign. A renewal is a natural place for the clock to get reset — you've spent five years paying a 25-year mortgage down to 20 years remaining, and the new offer quietly stretches it back out to 25. The rate might be identical. The payment is lower because the loan got longer.
What the reset actually costs
Take a $500,000 balance renewing at 4.19%, roughly where uninsured five-year fixed rates sit in late August 2026. Here's the same balance at the same rate, over a five-year term, under three amortizations:
| Amortization | Monthly payment | Interest paid over 5 years | Balance at end of term |
|---|---|---|---|
| 20 years | $3,071 | $95,061 | $410,825 |
| 25 years | $2,682 | $97,610 | $436,699 |
| 30 years | $2,432 | $99,251 | $453,352 |
Going back to 25 years saves you $389 a month. Over the five-year term it costs about $2,500 in extra interest — which is real but not dramatic.
The number that matters is the last column. At the end of the term you owe $25,874 more than you would have. That's not interest you paid; it's principal you didn't. The gap follows you into every renewal after this one, and if you run the full amortization to the end, the 25-year path costs $304,556 in lifetime interest against $236,944 for the 20-year — about $68,000.
The gap scales with the balance. On $350,000 the monthly difference is $272; on $700,000 it's $544.
The argument on the other side
There's a real counterargument, and it's mostly right: a longer amortization isn't a worse mortgage, it's a lower mandatory payment. Take the 25-year amortization, then voluntarily pay the 20-year amount, and the outcomes are not merely similar — they're identical to the dollar. Same interest, same balance, same date you're mortgage-free.
What you've bought with that structure is optionality. If the furnace dies or your hours get cut, you can drop to the $2,682 minimum for a while without asking anyone's permission or missing a payment. With a true 20-year amortization, $3,071 is the floor, and falling below it is a default.
Two things have to be true for this to work:
- Your prepayment privileges have to cover it. Replicating a 20-year amortization from a 25-year base means increasing your payment by 14.5%. From a 30-year base it's 26.3%. Most lenders allow an annual payment increase of 10% to 20% — so the 25-year version usually fits, and the 30-year version often doesn't. Check the number in your commitment letter, not the brochure.
- You have to actually do it. The lower payment is automatic. The extra is a choice you have to keep making every month for twenty years. Be honest about which kind of household you run.
What to check before you sign
- Find the amortization on the offer. It's on the commitment letter, not buried — but it's easy to skim past when you're comparing rates. If the payment dropped and the rate barely moved, the amortization changed.
- Compare balances, not payments. Ask each lender what you'll owe at the end of the term. That single number makes the offers comparable in a way monthly payment never does.
- Ask for the prepayment terms in writing. Annual lump-sum limit, payment increase limit, and whether unused room carries forward.
- Decide deliberately, not by default. Choosing a longer amortization for breathing room is a reasonable plan. Getting one because you didn't read the offer is not.
The takeaway
A longer amortization is a tool, not a trap — but it should be something you chose, with a plan for the extra payment, rather than something you discovered three years later. Before you sign, run the new payment through the house poor calculator to see what share of your take-home pay it eats at both the minimum and your target payment, and check the home affordability calculator if your income has moved since you last qualified.
Payment and interest figures calculated at 4.19% using the Canadian semi-annual compounding convention. Rate reflects average five-year fixed offers as of August 27, 2026 per Ratehub and WOWA. The Bank of Canada's next policy rate announcement is September 2, 2026.