Key Takeaways
- Cash damming sends the rent you collect against the debt on your home and pays the rental's expenses with funds borrowed from a separate line of credit used for nothing else.
- Your personal-use debt goes down faster. The rental line grows by the rental bills it paid. Total debt stays roughly level; what it was used for changes.
- Section 20(1)(c) of the Income Tax Act looks at the direct use of borrowed money, so every borrowed dollar needs a clear paper trail.
- It tends to fit landlords with a personally held rental, personal-use debt on their home and a product that readvances to a linked line of credit.
What Is Cash Damming?
Cash damming is a debt strategy for Canadian landlords. The rent you already collect becomes an additional prepayment on your home mortgage, and the rental property's expenses are paid with funds borrowed from a separate line of credit used for nothing else.
Same rent, same bills. What changes is which account pays which bill.
Each month, your personal-use debt drops by the rent you prepaid, and the rental line rises by the rental bills it covered. Over time, personal-use debt is replaced by rental-use borrowing. That shift is the whole idea.
You will also see it called rental cash damming or the Cash Flow Dam. The name comes from the Smith Manoeuvre: you dam the rent before it flows to the rental's bills and send it to your personal-use debt instead.
For the complete strategy, including the rules and the setup, read our rental cash damming guide.
The Problem It Addresses: Personal-Use Debt Gets Paid Last
Most landlords carry two kinds of debt. There is the debt on the home they live in, and the debt on the rental they own.
By default, the money flows like this. Rent pays the rental's bills. Your salary, after tax, pays down the debt on your home.
That order puts your most expensive debt last. The debt on your home is personal-use borrowing. You borrowed to buy a place to live, so its interest is not deductible, however large the balance.
The cost adds up. On $600,000 of personal-use debt at 4.5%, the first year's interest is about $26,000, all of it paid with after-tax dollars.
Rental expenses are different. Property tax, insurance, condo fees, repairs and the payments on the rental's own borrowing are paid to earn rental income. Interest on money borrowed for that purpose may be deductible, depending on the requirements of the Income Tax Act and your circumstances.
Cash damming connects the two flows. Rent goes to the personal-use debt; rental bills are paid with borrowing used only for the rental.
The Basic Mechanic
Cash damming runs on a fixed monthly routine and a set of dedicated accounts. In short:
- Rent lands in a rental income account. Tenants pay into an account that does nothing else.
- Rent is prepaid against the debt on your home. The full rent goes over as an additional prepayment.
- Borrowing room opens up. With a readvanceable product, the principal you just prepaid becomes available again on a linked line of credit.
- The rental line funds a rental expense account. You draw only what the rental's bills need.
- The expense account pays the rental bills. Every rental bill, including the interest on the line, is paid from that account, never straight from the line.
Then it repeats. Most transfers can be scheduled; the monthly prepayment is usually the one step done by hand.
The product must readvance to a linked line of credit, with a separate line used only for rental expenses. Whoever handles your mortgage confirms whether yours supports it, and we coordinate with them.
For the account structure, the sequence and the record keeping in detail, read how rental cash damming works.
Why the Use of the Money Matters
Section 20(1)(c) of the Income Tax Act deals with interest on money borrowed for the purpose of earning income from a business or property. Rental income is income from property.
The test looks at what the borrowed money was actually used for, not what secures the loan. The Supreme Court of Canada's 1987 decision in Bronfman Trust is the leading case on that direct-use test: the court looked at how the borrowed money was used directly, not at indirect benefits.
So a line of credit secured on your home, used only to pay a rental's expenses, may be considered to have been used to earn rental income. Whether interest on it may be deductible depends on your facts and your records.
CRA's Income Tax Folio S3-F6-C1, Interest Deductibility, discusses how borrowed money is traced to its use and how separate accounts keep that trail clear. That guidance explains how CRA reads the law. It is not approval of any plan or any implementation.
This is why the separate accounts and the order of each transfer matter so much. One personal purchase on the rental line, or one bill paid straight from the line, makes the trail harder to follow. For the rules and the cases in full, read is rental cash damming legal in Canada.
A Simple Example
Assumptions:
- Personal-use debt on your home: $600,000 at 4.5%
- One rental: $2,500 a month in rent
- Rental expenses, including the payment on the rental's own borrowing: $2,500 a month
Without cash damming: the $2,500 in rent pays the $2,500 in rental bills. The debt on your home comes down only through its regular payments.
With cash damming: funds borrowed from the rental line pay the $2,500 in rental bills. The full $2,500 in rent goes against the debt on your home as an additional prepayment.
Over a year, that is $30,000 of extra principal off your personal-use debt. The rental line grows by $30,000 of rental-use borrowing, plus the interest paid from it.
Total debt is about the same. The difference is what each dollar of it was used for.
Your own numbers will differ. Rent, expenses, rates and the time left on your debt all change the picture, which is why we model it on your figures before you start.
What Cash Damming Is Not
A few misunderstandings come up often.
It is not new debt on its own. Debt shifts from personal use to rental use; the total stays roughly level. The exception is a cash-flow-negative rental, where the line pays more in bills than the rent prepays, so the rental-use balance can grow faster than your personal-use debt falls.
It is not investing. Cash damming pays real rental bills you already have. There is no portfolio and no market exposure, unlike the Smith Manoeuvre.
It is not a new income source. Your rent and expenses stay the same. Only the route the money takes changes.
It does not remove risk. If personal spending lands on the rental line, or receipts go missing, CRA may deny the interest and reassess, with interest and possible penalties.
It is not a one-time setup. It needs separate accounts, a monthly prepayment and clean records for as long as it runs.
Who Cash Damming Fits
Cash damming tends to fit landlords who:
- Own at least one rental property personally, not inside a corporation
- Carry personal-use debt on the home they live in, with at least 15 years left to pay it
- Have a household income above about $75,000
- Have a readvanceable product, or can get one
- Live outside Quebec, which has its own tax legislation
The rental can be a house, condo, multi-unit or basement suite. A suite in your own home needs more care, because shared costs are split between the rented part and the part you live in.
The rental does not have to be cash-flow positive. With a negative rental, funds borrowed from the line pay the expenses rent does not cover, and you stop topping it up from your own pocket. The rental-use balance grows faster, so we model that shortfall on your numbers before you commit.
It is usually a poor fit if you plan to sell the rental in the next few years, if your personal-use debt is nearly paid off, or if you are not prepared to keep separate accounts and monthly records. Rentals held in a corporation don't fit the setup described here.
See the full checklist: who qualifies for rental cash damming.
Cash Damming vs the Smith Manoeuvre
Cash damming uses rental expenses to change what your debt is used for, and it needs a rental property.
The Smith Manoeuvre needs no rental. It reborrows the principal you pay down on your home and invests it. That is leveraged investing, and markets fall as well as rise. If you already hold non-registered investments, a debt swap is a related approach.
The two can run together. Read the full comparison of cash damming vs the Smith Manoeuvre.
What Freedom10 Delivers
The accounts, the monthly sequence and the record keeping need to be designed before the first dollar moves. A setup error does not just shrink the benefit; it can muddy the trail the strategy depends on.
We design the strategy together and help you set it up, implement it and track it. You run it. Here is what you get:
- A custom plan with step-by-step instructions, a money-flow flowchart, your bank account structure and a transaction map
- A video call walking you through the plan line by line
- A setup checklist so you know what to set up and in what order
- A Google Sheets tracking sheet
- Twelve months of support: up to three 30-minute calls a month for the first 90 days, then one a month
- Up to one hour with your own accountant at tax time
Setup usually takes four to six weeks. After that, most of the monthly transfers can be automated, and you follow the checklist.
See What Your Debt Could Be Doing
Watch our free masterclass. We walk through cash damming step by step with worked examples, from the first rent payment to the monthly records.
This article is for educational purposes only and is not tax, legal or financial advice. Freedom10 does not prepare tax returns or give personalized tax advice, and how the strategies described here apply to you depends on your facts. You should always seek independent tax advice if you are thinking about implementing these strategies. Freedom10 is a financial strategy and education company.