Cash Damming for Ontario Rental Owners
Same money owed, different interest. Cash damming moves debt from the side of your balance sheet where interest is not deductible to the side where it is — using the rent you already collect.
What it actually is
Cash damming is a bookkeeping discipline, not a product. Nothing is sold to you and no new money is created. You simply stop paying rental costs out of your own pocket, and start paying them from borrowed money that is earmarked for the rental — which frees the rent to attack your personal mortgage instead.
It is the sibling of the Smith Manoeuvre. The Smith Manoeuvre re-borrows principal to invest; cash damming re-borrows to carry rental expenses. Most rental owners who use one end up using both.
The four moves, in order
1. Set up the plumbing at renewal or refinance.
Cash damming needs a readvanceable mortgage — a mortgage with a credit line attached that grows as the principal comes down. That structure goes in at renewal or refinance. You cannot bolt it on mid-term.
2. Pay every rental expense from the credit line.
Property taxes, insurance, repairs, condo fees, property management, the rental mortgage interest itself. Those costs come out of the credit line segment reserved for the rental — never from your personal chequing account.
3. Send the rent against your non-deductible debt.
Because the expenses are being carried by the credit line, the rent is free to go where it does the most good: against the mortgage on your own home, where the interest is not deductible.
4. The balance shifts from non-deductible to deductible.
Month by month, personal mortgage debt shrinks and rental-purpose credit line debt grows. The total owed barely changes. What changes is which portion of the interest your accountant can deduct against rental income.
A worked illustration
$1,900/mo rent collected
$1,300/mo rental expenses paid from the credit line
$1,900/mo applied to the personal mortgage instead
After 12 months: ≈ $15,600 of non-deductible debt converted to rental-purpose debt
Illustration only. Your numbers depend on the rent, the expenses, the structure your lender will approve, and what your accountant confirms is deductible.
Non-negotiable rules
- One segment or sub-account per purpose. Borrowed money for the rental never touches personal spending.
- Every dollar must be traceable to a rental expense — keep the invoices, not just the statements.
- The property has to actually produce income. A vacant or personal-use property does not qualify.
- Your accountant confirms deductibility before the structure funds, not at tax time.
Model your own rental
Put in the rent and the annual expenses to see how much debt shifts per year, and how long the conversion would take at your numbers.
What rental cash damming actually does
Rental cash damming is a Canadian tax-restructuring technique for landlords. Each month the rental income is redirected as a lump-sum prepayment against the personal (non-deductible) mortgage, while a line of credit is drawn to cover the rental property's operating costs — property tax, insurance, utilities, repairs, condo fees.
Because those HELOC dollars are now being used for a genuine income-earning purpose, the interest on that HELOC balance may be deductible against your rental income under paragraph 20(1)(c) of the Income Tax Act. The total household debt stays roughly the same, but its character changes — the personal mortgage shrinks and the potentially deductible HELOC grows.
No investment risk is introduced — outcomes depend on rental income, mortgage rate, HELOC rate and your marginal tax rate. The strategy does require a re-advanceable mortgage and strict segregation of the two accounts.
Your numbers
Mortgage after 10 yrs
$0
Without strategy: $439,666
HELOC balance
$160,404
Interest accrued: $46,404
Estimated tax recovery
$19,954
Extra principal paid: $600,000
Assumes Canadian semi-annual mortgage compounding, that the HELOC is used strictly to pay documented rental expenses, that interest is capitalised on the HELOC, and that any tax recovery is applied annually as a lump-sum prepayment against the personal mortgage. Confirm eligibility, tracing requirements and property-specific tax treatment with a qualified CPA and licensed mortgage professional before implementing.
About rental cash damming in Canada
Rental cash damming is a Canadian tax-restructuring technique used by landlords who also carry a non-deductible personal mortgage. Each month, gross rental income is redirected as an extra prepayment against the personal mortgage, while a separate line of credit — typically a HELOC or a segregated re-advance sub-account — is drawn to pay the rental property's legitimate operating expenses such as property tax, insurance, utilities, repairs and condominium fees.
Because those HELOC dollars are now being used for a genuine income-earning purpose tied to the rental property, the interest on that HELOC balance may be deductible against the rental income under paragraph 20(1)(c) of the Income Tax Act. The total household debt stays roughly the same, but its character shifts: the personal (non-deductible) mortgage shrinks faster and the potentially deductible HELOC grows. No investment risk is added, but the strategy depends on strict account segregation, defensible tracing and eligible rental expenses.
Cash damming is not automatically available. Whether the interest is deductible depends on the current-use of the borrowed funds, whether the expenses paid from the HELOC are themselves deductible rental expenses, and on your ability to document each transaction. A CPA familiar with rental real estate should confirm eligibility, the correct account structure and the recordkeeping standard your lender and the CRA will accept.
Frequently asked questions
Educational use only — please read
The Rental Cash Damming Calculator is provided by The Juneja Group strictly for general education and illustration. It is not tax, legal, accounting or investment advice, is not a recommendation to enter into any strategy, and does not create an advisor–client relationship. The outputs are simplified projections based on the numbers you enter and standard assumptions — real-world results will differ.
The rules that determine whether interest is deductible, how capital gains are treated, how rental income and expenses must be tracked, and whether a strategy is appropriate for your situation are governed by the Income Tax Act (Canada), CRA administrative positions and your provincial rules — all of which change over time. Nothing on this page should be relied on in place of a written opinion from a qualified professional.
Before acting, consult a Canadian Chartered Professional Accountant (CPA) and a licensed mortgage professional who can review your full picture — income, other debts, family situation, risk tolerance, cash-flow stability, existing registered accounts and estate plan. Ask them to model your specific numbers, the downside scenarios and the record-keeping/tracing requirements before you commit.
Need a referral? If you don't already have a CPA or tax lawyer you trust, contact The Juneja Group and we're happy to refer you to independent professionals other clients have recommended. We do not accept referral fees from them, and any engagement you enter into is directly with that professional.
Mortgage advice only. Cash damming is an advanced strategy and the deductibility of interest depends entirely on CRA tracing rules and your own circumstances. Engage a licensed CPA before implementing anything on this page.
The structure has to go in at the right moment
Readvanceable mortgages get set up at renewal or refinance. If your renewal letter has arrived, this is the window.