The core question
You have an extra $500/month. Should you:
A) Put it toward your mortgage to pay it off faster? B) Invest it in your TFSA, RRSP, or non-registered account?
The answer depends on exactly three things:
- Your mortgage interest rate (your cost of debt).
- Your expected after-tax investment return (your return on capital).
- Your risk tolerance (your comfort with uncertainty).
The mathematical comparison
Scenario: $400,000 mortgage at 5%, 25-year amortization
$500/month extra — invested vs. mortgage prepayment over 15 years
| Strategy | Total extra payments / contributions | Mortgage balance at year 15 | Investment balance at year 15 | Net wealth gain |
|---|---|---|---|---|
| Pay mortgage faster | $90,000 in extra payments | $0 (paid off at year 16.5) | $0 | $108,000 in saved interest |
| Invest (5% return, taxable) | $90,000 invested | $196,000 remaining | $134,000 | $134,000 portfolio |
| Invest (7% return, TFSA) | $90,000 invested | $196,000 remaining | $158,000 | $158,000 portfolio |
At a 5% mortgage rate and a 7% TFSA return, investing beats mortgage prepayment by approximately $50,000 over 15 years.
But if the mortgage rate is 6.5% and investments return only 5% after tax, prepayment wins.
The breakeven rule
If your after-tax investment return > your mortgage rate → invest. If your after-tax investment return < your mortgage rate → pay down mortgage.
| Mortgage rate | After-tax return needed to beat prepayment |
|---|---|
| 3.0% | > 3.0% (easy in most environments) |
| 4.0% | > 4.0% (achievable with balanced portfolio) |
| 5.0% | > 5.0% (moderate — TFSA needed for tax efficiency) |
| 6.0% | > 6.0% (difficult — prepayment often wins) |
| 7.0%+ | > 7.0% (very difficult — prepayment almost always wins) |
Tax treatment matters enormously
Mortgage interest is NOT deductible in Canada
Unlike the US, Canadian homeowners cannot deduct mortgage interest on their principal residence. This means your mortgage rate is your true after-tax cost.
- 5% mortgage rate = 5% after-tax cost
- There’s no tax benefit to keeping the mortgage
Investment returns ARE taxable (unless sheltered)
| Account type | Tax on returns | Effective after-tax return (assuming 7% pre-tax, 30% marginal rate) |
|---|---|---|
| TFSA | None | 7.0% |
| RRSP | Deferred (taxed on withdrawal) | ~5.5–6.5% (depends on withdrawal tax rate) |
| Non-registered (interest) | Fully taxable | ~4.9% |
| Non-registered (Canadian dividends) | Dividend tax credit | ~5.6% |
| Non-registered (capital gains) | 50% inclusion | ~5.9% |
The TFSA is the clearest winner — a 7% return is a true 7%, easily beating a 5% mortgage. Non-registered interest income at 4.9% after tax barely beats a 5% mortgage, if at all.
The guaranteed vs. uncertain return
Mortgage prepayment = guaranteed return
Every extra dollar paid on your mortgage earns a guaranteed, risk-free return equal to your mortgage rate. If your rate is 5%, prepayment gives you a guaranteed 5% return. No market can guarantee that.
Investing = expected (but uncertain) return
Historical Canadian balanced portfolio returns average ~6–8% annually over long periods. But:
| Period | Balanced portfolio (60/40) return | Would investing have beaten a 5% mortgage? |
|---|---|---|
| 2000–2009 | ~4.5% annually | No |
| 2010–2019 | ~8.5% annually | Yes |
| 2020–2024 | ~6.5% annually | Marginally yes |
| Long-term (30+ years) | ~7.0% | Yes |
Over any single 5-year period, there’s a 20–30% chance that a balanced portfolio underperforms a 5% mortgage. Over 15–20 years, the probability drops below 10%.
Time horizon matters: The longer your investing horizon, the more likely investing beats prepayment. If you’ll invest for 5 years or less, the guaranteed mortgage prepayment is safer.
The risk tolerance framework
| If you… | Lean toward… | Why |
|---|---|---|
| Sleep poorly when markets drop | Mortgage prepayment | Guaranteed return, no volatility |
| Are comfortable with a 20% portfolio drop | Investing | Higher expected long-term return |
| Have a short time to retirement (< 10 years) | Mortgage prepayment | Less time to recover from market losses |
| Have a long time horizon (15+ years) | Investing | Historical odds heavily favour investing |
| Have no emergency fund | Mortgage prepayment (or build emergency fund first) | Liquidity risk — investments can be sold in a downturn |
| Have a high mortgage rate (6%+) | Mortgage prepayment | Hard to beat 6%+ guaranteed return |
| Have a low mortgage rate (< 4%) | Investing | Easy to beat in almost any account type |
| Have unused TFSA room | Investing (in TFSA) | Tax-free returns almost certainly beat mortgage rate |
The hybrid approach (optimal for most Canadians)
Pure math says invest. Pure peace-of-mind says pay down the mortgage. The hybrid approach captures both benefits.
Recommended priority order
| Priority | Action | Rationale |
|---|---|---|
| 1 | Max employer RRSP match | Free money — 50–100% instant return |
| 2 | Build 3-month emergency fund | Prevents high-interest debt if something goes wrong |
| 3 | Max TFSA contributions | Tax-free returns beat mortgage rate in most environments |
| 4 | Split remaining 50/50 between RRSP and mortgage prepayment | Balances tax deferral with guaranteed debt reduction |
| 5 | Once TFSA and RRSP maxed, prepay mortgage | Guaranteed return, no tax advantage to investing in non-registered if rate is 5%+ |
Worked example: $1,000/month extra cash
| Allocation | Amount | Expected annual return | Annual benefit |
|---|---|---|---|
| TFSA (balanced ETF portfolio) | $583/month ($7,000/year) | 7% tax-free | $490 in growth (growing annually) |
| Mortgage prepayment | $417/month | 5% guaranteed | $250 in saved interest (year 1, growing) |
| Total | $1,000/month | $740 combined benefit |
Over 15 years, this hybrid approach:
- Builds a $175,000+ TFSA portfolio (tax-free).
- Pays off the mortgage 4+ years early.
- Saves $45,000+ in interest.
- Provides a liquid emergency buffer (the TFSA) alongside a shrinking debt (the mortgage).
The RRSP angle: Smith Manoeuvre
For higher-income Canadians ($100,000+), the Smith Manoeuvre can make investing even more attractive.
How it works
- Make regular mortgage payments.
- Re-borrow the principal portion through a readvanceable mortgage (HELOC that grows as mortgage shrinks).
- Invest the borrowed funds in a non-registered account.
- Deduct the interest on the borrowed-to-invest funds (because the purpose is investment, the interest becomes tax-deductible).
- Use tax refunds and investment income to accelerate mortgage paydown.
Simplified math
| Without Smith Manoeuvre | With Smith Manoeuvre |
|---|---|
| $400,000 mortgage at 5% | $400,000 mortgage at 5% |
| Interest cost: $20,000 (year 1) | Interest cost: $20,000 (year 1) |
| Tax deduction: $0 | Tax deduction on HELOC interest: ~$5,000 (at 30% rate = $1,500 saved) |
| Investment returns: $0 | Investment returns: ~$16,000 (on borrowed $230,000 invested, at 7%) |
Caution: The Smith Manoeuvre adds complexity and risk. Borrowed-to-invest strategies amplify both gains and losses. Consult a financial advisor and tax professional before implementing.
Mortgage prepayment options
If you decide to accelerate your mortgage, understand your options:
| Prepayment method | How it works | Impact (on $400,000, 5%, 25-year) |
|---|---|---|
| Increase payment frequency | Switch from monthly to accelerated bi-weekly | Saves $34,000, pay off 2.5 years early |
| Lump-sum payment | Annual prepayment (most lenders allow 10–20% of original principal) | $40,000 lump sum saves ~$60,000 in interest |
| Increase regular payment | Raise payment by 10–20% (most lenders allow annually) | +$200/month saves $55,000, pay off 5 years early |
| Round up payments | Increase from $2,311 to $2,500 | +$189/month saves $49,000, pay off 4.5 years early |
Check your mortgage contract for prepayment privileges. Fixed-rate mortgages typically allow 10–20% annual lump sum and 10–20% payment increase without penalty. Variable mortgages often have more flexible terms.
Scenario analysis by rate environment
Low-rate environment (mortgage 3–4%)
| Strategy | 15-year outcome (on $500/month) |
|---|---|
| Prepay mortgage (3.5%) | Save $62,000 in interest |
| Invest in TFSA (7%) | Grow to $158,000 |
| Winner | Investing by $96,000 |
Mid-rate environment (mortgage 5–6%)
| Strategy | 15-year outcome (on $500/month) |
|---|---|
| Prepay mortgage (5.5%) | Save $118,000 in interest |
| Invest in TFSA (7%) | Grow to $158,000 |
| Winner | Investing by $40,000 (but narrower margin) |
High-rate environment (mortgage 7%+)
| Strategy | 15-year outcome (on $500/month) |
|---|---|
| Prepay mortgage (7%) | Save $145,000 in interest |
| Invest in TFSA (7%) | Grow to $158,000 |
| Winner | Nearly tied — prepayment wins on a risk-adjusted basis |
The higher the mortgage rate, the more compelling prepayment becomes — because the guaranteed return rises while investment returns are uncertain.
Decision summary
| Your mortgage rate | TFSA room available? | Recommended approach |
|---|---|---|
| Under 4% | Yes | Invest in TFSA. Mortgage prepayment is low priority |
| Under 4% | No (maxed) | Invest in RRSP or split with prepayment |
| 4–5.5% | Yes | TFSA first, then hybrid (50/50 RRSP and prepayment) |
| 4–5.5% | No | Hybrid — split between RRSP and prepayment |
| 5.5–7% | Yes | TFSA first (still beats mortgage rate), then prepayment |
| 5.5–7% | No | Lean heavily toward prepayment |
| 7%+ | Any | Prioritize mortgage prepayment (guaranteed high return) |