Homes & mortgages
Extra mortgage payments or investing: compare the same money
Understand interest avoided, uncertain growth and the value of accessible cash.
The key idea
Compare alternatives using the same starting money, ongoing funding and period. A mortgage prepayment reduces debt; an investment contribution buys an asset. Neither transfer creates an immediate profit simply by moving the money.
Make the funding comparable
Start after required payments and essential costs. Decide whether you are comparing an existing lump sum or future monthly money. Do not give one alternative both. Keep a reserve or near-term spending goal visible, especially when the money could be needed before an investment can be sold.
What each alternative changes
A permitted prepayment lowers principal and therefore can avoid later interest. Contract limits, charges and the inability to simply take the money back matter. Compare the actual borrowing schedule; future renewal rates may differ. FCAC: paying off your mortgage faster
Investing leaves an asset whose value can rise or fall. Fees, taxes, liquidity and holding type affect the outcome. A TFSA or RRSP name does not itself supply a return. FCAC: basics of investing
Read the result without adding gains twice
If a model already shows a lower remaining debt, do not add all the principal reduction again as a separate gain. Likewise, a projected investment balance includes the money you contributed. Compare accessible cash, debt and investment value consistently, while keeping omitted home value and taxes explicit.
There is no default split
A one-third allocation has no special claim to suitability. A household may need the entire amount for a repair, a reserve, debt or spending on life now. If there is no surplus, the next task is addressing the funding gap, not choosing an investment allocation.
See it in practice
Moving $1,000 does not make $1,000 of profit
| Position | Cash | Investment | Debt |
|---|---|---|---|
| Before | $1,000 | $0 | $100,000 |
| Prepay principal | $0 | $0 | $99,000 |
| Invest instead | $0 | $1,000 | $100,000 |
Cash + investments − debt equals −$99,000 in every row. The later paths can differ through interest, returns and costs. Home value and all other assets/debts are excluded, so this is not complete household net worth.
Check your understanding
Is the entire final investment balance a return?
No. It includes starting money and later contributions. Only the change after separating those flows and costs describes growth.
A useful next step
Write the same funding amount and dates for both options. The Decision Lab beta can illustrate a generic investment/extra-principal experiment. Investment results are after entered fees and before personal taxes; registered-account rules, lender permissions and home value are not included.
Inspect the sources
Primary references checked September 18, 2026. A source check is not professional financial or legal review.
- FCAC: paying off your mortgage fasterCurrent at check · Canada; contract-specific
- FCAC: basics of investingConceptual; checked 2026 · Canada; provincial securities regulation