What is capitalized interest?

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Capitalized interest is interest you pay by borrowing more, rather than paying it in cash. The outstanding interest is added to your loan balance and becomes new principal — so your debt grows, but no cash leaves your account. You then pay interest on that larger balance going forward.

This is common in Smith Manoeuvre strategies, where the goal is to keep cash invested rather than using it to pay interest.

Credit-line capitalization, step by step

For credit-line interest, capitalization means paying outstanding interest by borrowing more from your credit line. This applies when your lender added interest to the credit balance and you settle that outstanding interest by borrowing more from the same account.

How lenders charge interest

How you capitalize depends on how your lender charges interest:

Interest added to your credit balance. Some lenders add accrued interest directly to your HELOC balance. The interest sits as an outstanding charge until paid. To capitalize, first record an Interest Charge, then an Interest Capitalization to settle the outstanding interest by borrowing more from the same account.

Interest charged to an external account. Other lenders debit interest from an external chequing or savings account. The interest never appears as outstanding interest on the credit-line balance. If you paid it from personal funds, record only an Interest Charge in “Charged to external account” mode. If you funded that payment from the credit line, stay in the same Interest Charge workflow and enter the credit-line transfer details there. The app treats the charge and funding transfer as one combined event for balance-calculation purposes.

Interest Capitalization events are only used for the first case: interest added to the credit balance. External-account capitalization is handled inside the Interest Charge event.

How character is inherited

When you capitalize interest, the new principal takes on the character of the interest it paid:

• Deductible interest paid by capitalization becomes capitalized deductible principal — and interest charged on it is itself deductible
• Non-deductible interest paid by capitalization becomes capitalized non-deductible principal — and interest on it remains non-deductible

If you have a mix of outstanding deductible and non-deductible interest, capitalization is applied proportionally — just like credit payments.

Worked example

For a lender that adds interest to the credit balance, you have $150 in outstanding interest: $120 eligible (deductible), $30 non-eligible. You capitalize the full amount.

• Outstanding eligible interest: $120 → $0 (paid)
• Outstanding non-eligible interest: $30 → $0 (paid)
• Capitalized deductible interest: +$120 (new principal)
• Non-deductible principal: +$30 (capitalized non-deductible interest)
• Total debt: unchanged ($150 of interest became $150 of principal)

For tax purposes, you paid $120 of deductible interest — even though no cash left your pocket. That $120 counts toward your deductible interest for the year.

Here's how this looks in the app's event detail view:

Why capitalize?

Cash flow management: Keep your cash invested rather than using it to pay interest. This is central to many Smith Manoeuvre implementations.

Tax timing: Capitalizing interest makes it deductible in the year of capitalization. December interest that would otherwise be paid in January can be capitalized in December to accelerate the deduction.

Compound leverage: Capitalized interest becomes principal that itself accrues interest. This is leveraged compounding — your debt grows, but so does your invested capital if you reinvest.

The Smith Manoeuvre connection

The Smith Manoeuvre converts non-deductible mortgage interest into deductible investment loan interest. Many implementations use a readvanceable HELOC and capitalize the investment interest:

1. Each mortgage payment increases available HELOC credit
2. Borrow from HELOC to invest
3. Capitalize the investment interest rather than paying cash
4. Over time, non-deductible mortgage debt converts to deductible investment debt

CRA basis

Interest is deductible when paid, per Income Tax Folio S3-F6-C1. Capitalizing interest is a form of payment — you're using borrowed funds to discharge the interest obligation. Paragraph 1.38 notes that interest on borrowed money used to pay deductible interest is itself deductible.

Related topics

• Mixed HELOC use — capitalization follows the same proportional rules as payments
• How interest is time-weighted — how capitalized principal affects future interest charges
• How interest deductibility works — the core concept