If you run an incorporated business in Canada, tax is almost certainly your single biggest lifetime expense — larger than your mortgage, larger than payroll. And the tax system is, at its core, a rulebook: a set of rules the government uses to encourage certain behaviour. The job is to learn the rules and play by them. In an interview, Michael Baker, CPA, framed every tax decision a business owner faces around four levers — what he calls the 4 Ds: Deduct, Divide, Defer, and Decrease.
The reason the 4 Ds matter so much comes down to one number. Active business income under the $500,000 small-business limit is taxed at a combined federal-provincial rate of roughly 9–13%, depending on your province. Income above that limit is taxed at the general rate — roughly 23–31%. That gap is the prize the 4 Ds help you protect and use.
1. Deduct
The first lever is the most familiar: claim every legitimate deduction and allowance available to you. Vehicle costs, a home-office allowance, eligible business expenses, capital cost allowance on equipment — the list is long and province- and industry-specific. A good accountant knows exactly what you can deduct and, just as importantly, where the line is. The goal isn’t to be aggressive; it’s to make sure you’re not leaving legitimate money on the table.
2. Divide
The second lever is income splitting — moving income to family members in lower tax brackets so the household pays less overall. The big caveat: the Tax on Split Income (TOSI) rules, in force since 2018, sharply limit this. The old playbook — simply paying a spouse or adult child a dividend — generally no longer works unless that person is genuinely active in the business (or meets one of the specific exclusions, such as being 65+ or holding qualifying shares). Splitting is still possible in defined situations, but it has to be structured carefully and reviewed. This is not a do-it-yourself lever.
3. Defer
The third lever is the quiet powerhouse, and it’s the one owners most often underuse. Because income kept in the corporation is taxed at the low small-business rate, you have far more capital left to reinvest than if you’d paid it out and been taxed personally.
A quick example
Your corporation earns $100,000 of active business income. At a ~12% small-business rate, the company keeps about $88,000 to reinvest. Take that same $100,000 out as salary and pay personal tax at, say, 45%, and you’re left with about $55,000 personally. That roughly $33,000 difference is capital that stays at work inside the company. Deferral is about timing, not avoidance — you’ll pay personal tax when you eventually take the money out — but as Mike puts it, the biggest factor in building wealth is time, and that head start compounds.
4. Decrease
The fourth lever is using income that’s taxed more lightly. Capital gains are included in income at a 50% inclusion rate — and that rate held steady for 2026 after the proposed increase to 66.67% was cancelled in 2025. Dividends are taxed at lower personal rates than salary thanks to the dividend tax credit. Tools like corporate-class funds, or simply tilting an investment portfolio toward growth rather than interest income, can change the character of your income and lower the rate. (How you pay yourself is its own version of this lever — see salary vs. dividends.)
How the 4 Ds work together
No single D wins on its own; a strong plan uses all four, coordinated across your accountant, lawyer, and insurance advisor — which, as Mike notes, is rare, because those professionals so seldom talk to each other. His bottom line: a good accountant should save you far more in tax than you’ll ever pay in fees. The 4 Ds are simply the map for finding where those savings are hiding.
Frequently asked questions
What are the 4 Ds of tax planning?
The 4 Ds are Deduct (claim every legitimate deduction), Divide (income splitting within the TOSI rules), Defer (keep income in the corporation at the low small-business rate to reinvest more), and Decrease (use lower-taxed income like capital gains and dividends). Together they form a framework for thinking through corporate tax decisions.
What is the small business deduction limit in Canada?
Active business income up to $500,000 a year qualifies for the small-business rate, roughly 9-13% combined federal and provincial depending on your province. Income above $500,000 is taxed at the general corporate rate, roughly 23-31%.
Are capital gains still taxed at the 50% inclusion rate in 2026?
Yes. The federal government proposed raising the capital gains inclusion rate to 66.67% in 2024, but the change was deferred and then cancelled in March 2025. For 2026, capital gains remain subject to the 50% inclusion rate. Confirm current rules with your accountant, as tax policy can change.
Can I still income-split with my spouse through my corporation?
Only in limited cases. The Tax on Split Income (TOSI) rules introduced in 2018 restrict paying dividends to family members unless they are genuinely involved in the business or meet a specific exclusion. The old approach of simply paying a spouse a dividend generally no longer works without careful planning.
Do I need an accountant to use the 4 Ds?
Yes. The 4 Ds work best when coordinated, and several of them (income splitting, deferral strategy, choosing income types) depend on your specific structure, province, and current-year rules. A CPA should save you more in tax than you pay in fees.
General information for Canadian incorporated business owners — not tax, accounting, or legal advice. Figures are current for 2026 and change yearly; tax outcomes depend on your province and situation. Confirm the details with your CPA before acting. Dundas Wealth operates as the brand of Dundas Life Inc. (FSRA #37628M).