Smith Manoeuvre risk: what happens if your HELOC rate rises

Smith Manoeuvre risk becomes much easier to understand when the HELOC rate rises. A strategy that looked disciplined at 4.50% can feel very different at 7.50%. The portfolio may be unchanged, the dividends may still arrive, and the tax deduction may still exist, but the monthly carrying cost is heavier.

That is the uncomfortable part of leveraged investing. The investor controls the decision to borrow. They do not control the future interest rate.

The Smith Manoeuvre uses investment debt, often through a readvanceable mortgage or HELOC, to build a taxable portfolio. If the borrowed money is used to earn income and the records are clean, interest may be deductible. But a deduction is only partial relief. It does not stop the bank from charging more interest when rates rise.

The risk is not just whether the strategy works on paper. It is whether the household can keep carrying it.

The Rate Shock Problem

Suppose a homeowner has a $150,000 investment HELOC used for a Smith Manoeuvre portfolio. At a 5.00% rate, annual interest is:

$150,000 x 5.00% = $7,500

At a 7.50% rate, annual interest becomes:

$150,000 x 7.50% = $11,250

That is an extra $3,750 per year, or about $312.50 per month. The tax deduction may reduce the after-tax cost, but it does not eliminate the cash-flow pressure.

If the household is in a 35.00% combined marginal tax situation, the tax value of the higher $11,250 interest cost could be about:

$11,250 x 35.00% = $3,937.50 tax reduction

That still leaves a net cost of about $7,312.50. If the portfolio yields 4.00%, a $150,000 portfolio might produce $6,000 of dividends before tax. The income may not fully cover the after-tax interest cost, especially if dividends are reinvested instead of withdrawn.

This is the core HELOC rate risk. The debt cost can move faster than the income plan.

Why Deductibility Does Not Remove The Risk

Interest deductibility is valuable, but it is not the same as having the interest paid for you. A deduction reduces taxable income. The actual benefit depends on the investor's marginal tax rate.

If someone deducts $10,000 of interest at a 25.00% combined marginal rate, the tax reduction is about $2,500. At a 45.00% combined marginal rate, the tax reduction is about $4,500. Same interest cost, different benefit.

That means a rate increase hurts every investor, but the after-tax pain differs. Higher-income investors may receive more tax relief. Lower-income investors may receive less. Retirees, people on parental leave, or workers with variable income may see the deduction become less valuable in a lower-income year.

The strategy also creates timing friction. Interest is paid monthly. Tax relief may arrive later through a return or instalment adjustment. A household still needs the cash flow to bridge that timing gap.

This is why the Tax Bracket Calculator can be useful context. The Smith Manoeuvre is not just an investment-return question. It is a marginal-tax-rate question and a cash-flow question.

Stress Testing The HELOC

A proper Smith Manoeuvre plan should be stress tested before it is started and again as the balance grows. The easiest test is to raise the HELOC rate by 2.00% and 3.00% and ask whether the household can still carry the debt.

Suppose the HELOC balance is $200,000.

The jump from 5.00% to 8.00% adds $6,000 per year of interest. If the household has no room in the monthly budget, the strategy may force them to sell investments, capitalize more interest, or stop reborrowing.

Selling during a market decline can be especially damaging. The investor may lock in losses while the loan remains. Capitalizing interest can preserve cash flow but increases the debt balance. Stopping the strategy can be sensible, but it changes the expected outcome.

The point of stress testing is not to predict rates perfectly. It is to know where the strategy becomes uncomfortable before the bank statement makes that decision for you.

Dividends Can Help, But They Are Not A Shield

Dividend income can offset some HELOC interest, but it is not guaranteed. Dividends can be cut. ETF distributions can change. A portfolio built for yield can take equity risk even while it pays monthly or quarterly income.

If a $200,000 portfolio yields 4.50%, it may produce $9,000 per year. At a 7.00% HELOC rate, interest is $14,000. The dividend income covers part of the cost, not all of it.

Some investors reinvest dividends to grow the portfolio faster. Others use dividends to pay HELOC interest. Reinvestment may improve long-term compounding, while using dividends for interest may improve short-term cash flow. Neither choice removes rate risk.

The most resilient plan has a buffer. That could mean emergency savings, lower leverage, extra monthly cash flow, or a rule to pause new borrowing when rates rise above a set level.

Use The Smith Manoeuvre Calculator

The Smith Manoeuvre Calculator lets you test HELOC rate assumptions before committing to the strategy. Run the base case, then increase the HELOC rate by 1.00%, 2.00%, and 3.00%. Watch the annual interest cost, tax savings, and net cash-flow requirement.

The useful question is not "does the ending balance look bigger?" The useful question is "can I survive the worst middle years?" A strategy can look attractive over 20 years and still fail if year four creates a cash-flow squeeze.

Use the calculator to find the rate where the strategy stops fitting the household budget.

Takeaway

HELOC rate risk is one of the central risks in the Smith Manoeuvre. A $150,000 loan costs $7,500 at 5.00%, but $11,250 at 7.50%. The extra $3,750 per year can change the entire feel of the plan.

Tax deductibility reduces the after-tax cost, but the value depends on the investor's marginal rate and does not erase the cash-flow burden.

The strategy should be stress tested before it is scaled. If a rate increase would force bad decisions, the borrowing level is probably too high.