Should I Prepay My Mortgage at Renewal or Invest in My TFSA?
A couple sat across from me last month with $65,000 and a renewal in 60 days. The answer is not as obvious as either side makes it sound.
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The husband wanted to pay down the mortgage. The wife wanted to max their TFSAs. They had been going back and forth about it for weeks and came in expecting me to settle it.
They were both right. And they were both missing something.
The husband did not know their lender capped prepayments at 15% of the original balance. They could not put the full amount in even if they wanted to. The wife assumed a lump sum would lower their monthly payment. It would not, unless they asked to re-amortize. And neither of them was asking the question that actually mattered:
What are we more likely to do wrong?
That is where most people lose money in this decision. Not in the rate comparison or the return calculation. In the execution.
What the math says
The return on prepaying your mortgage is simple and guaranteed. It equals your interest rate. If your rate is 4.29%, a lump-sum prepayment produces a guaranteed 4.29% return with no volatility, no taxes, and no sequence risk.
A TFSA invested in a diversified ETF has historically returned 7% to 8% annually over long periods. On paper, if your mortgage rate is below 5% and you have unused TFSA room, investing comes out ahead. The gap is real.
But the math assumes you invest immediately, stay invested through market drops, and leave the money alone. That is not how most people behave.
What you can actually prepay without penalty
Every Canadian mortgage has a prepayment privilege clause. The common standard is 20/20: up to 20% of the original balance as a lump sum per year, and up to a 20% increase in your regular payment. But lenders vary, and one detail most people miss:
The percentage is based on your original balance — not your current one
| Lender | Lump Sum Limit | Key Detail |
|---|---|---|
| TD | Unlimited ($100 min) | Most flexible of the Big 5 |
| BMO | 20% of original balance | Standard 20/20 |
| CIBC | 20% of original balance | Annual anniversary date |
| RBC | 10–15% of original balance | Most restrictive of the Big 5 |
| Scotia | 15% of original balance | Cumulative over the term |
| Monolines | 15–20% of original balance | MCAP, First National — varies by product |
Some lenders allow multiple smaller lump sums throughout the year. Others restrict you to one. If you are planning to move money in stages, this matters more than the rate comparison. If your lender only allows 10%, I would walk away.
Lump sum or lower payment: what actually changes
Most people assume that putting a lump sum against their mortgage will reduce their monthly payment. It will not, unless you specifically request a re-amortization.
What changes is your timeline. More of each subsequent payment goes toward principal, and your mortgage ends sooner.
$60K
Lump Sum
Applied to a $400K balance
4 yrs
Amortization Eliminated
18 yrs drops to ~14 yrs
$0
Payment Change
Monthly stays the same
On a $400,000 balance, a $60,000 lump sum at current rates does not change the monthly payment. It can drop your remaining amortization from roughly 18 years to around 14. Four years of payments eliminated. That is significant, and it happens without touching your monthly cash flow.
If you want a lower payment, you need to ask your lender to re-amortize at renewal. At renewal with your current lender, this is possible. Mid-term, it usually triggers a refinance penalty.
When prepaying is the clearer answer
The behavioral argument alone often settles this, but there are situations where prepaying wins on the math as well.
If your mortgage rate is above 5%, the gap between guaranteed savings and realistic investment returns shrinks to the point where the certainty of the prepayment is worth more than the theoretical upside of investing.
Prepay the Mortgage
- Guaranteed return equal to your interest rate
- No market risk, no taxes, no fees
- Harder to impulsively spend the money
- Eliminates monthly payment sooner
- Locks up liquidity — cannot access the cash
- Loses to TFSA math when rate < 4%
Wins when your rate is above 5%, you are near retirement, or you know the money will not stay invested.
Invest in a TFSA
- Historically 7–8% annual returns (equity ETFs)
- Tax-free growth inside the TFSA
- Liquidity — you can access the money
- Compounds over decades
- Not guaranteed — markets drop
- The money is easy to spend instead
Wins on pure math when rate < 4% — but only if you actually invest and stay invested.
If you are within 10 years of retirement, eliminating a $2,000 monthly payment changes what retirement looks like in a way that an extra $10,000 in portfolio returns does not. The payment removal is structural. The return difference is marginal.
And if you are honest with yourself that the money will not stay invested, the math is irrelevant. A guaranteed 4.29% that actually happens beats a theoretical 7% that does not.
The behavioral edge most people overlook
I have watched clients get excited about investing, put money into the market, then pull it out when it drops 10% to 15%. I have seen others never invest at all. The money sits in a savings account for months, then gradually gets absorbed by things that felt important at the time. Something always comes up.
When the same money goes into your mortgage, it becomes harder to recover impulsively. You cannot transfer it to a chequing account with two clicks. That friction is not a limitation. It is protection.
As my book From Debt to Zero puts it: "The best mortgage you will ever have is the one with a zero balance." That is not just a philosophical point. It is a behavioral one. Consistent mortgage prepayments frequently outperform inconsistent investing in real life, even when the math says investing should win.
The timing detail almost nobody uses
Here is a practical point that rarely comes up in this conversation.
A lump sum applied on your renewal date counts toward the new term's prepayment privileges, not the old term. That means your prepayment limit resets on that date. If you have already used your full prepayment room during your current term, your renewal date is your reset button. You can apply a large lump sum on that exact date, have it counted against the fresh limit, and have your new rate applied to the lower balance from the first payment forward.
Some lenders will allow you to apply the lump sum directly as part of the renewal paperwork. Ask your lender specifically whether this is available. Most do not bring it up unprompted.
Splitting the strategy
You can divide the money, putting half toward the mortgage and half into a TFSA. This gives you both the guaranteed return and market exposure.
The honest condition for this to work
Splitting works for people who are already disciplined investors and genuinely want both outcomes. For everyone else, one clear strategy executed consistently beats two strategies executed partially.
The question that usually settles it
When clients come to me with this decision, I do not answer right away. I ask two questions.
If you invested the $60,000 and it dropped 15% in the first year, what would you do? And if it dropped another 10% the year after that?
Then:
If the same money were sitting in your TFSA right now, how easy would it be to spend it on something else over the next 12 months?
Most people answer their own question at that point.
This decision is not really about rates and returns. It is about behavior under pressure and how your financial decisions hold up when circumstances change. The right answer is the one you will actually follow through on, not the one that produces the best number in a spreadsheet.
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Camilo Rodriguez
Founder of Mortgages Lab & Mortgage Expert
Camilo Rodriguez is the Founder of Mortgages Lab, a licensed mortgage broker with over 23 years of experience helping Canadians achieve financial freedom. He has trained 100+ mortgage agents across Canada and is Past President of The Canadian Mortgage Broker Association - BC. He is the author of "From Debt to Zero," a guide to becoming mortgage free.
P.A.Y.O.F.F™, L.A.B™, M.A.P™ are Trademarks of Mortgages Lab®
Financial Disclosure
This page contains informational content only and does not constitute financial advice. Mortgage rates shown are sourced from publicly available lender data and may change without notice. Always verify rates directly with the lender. Mortgages Lab may receive compensation from partner lenders, which does not influence our editorial content or rate rankings. Built on Real Experience — 23+ years of working with real mortgage scenarios and helping Canadians achieve financial freedom.
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