Introduction

A newly licensed professional in Ontario starting their practice faces an immediate structural decision: incorporate, or operate as a sole proprietor? The answer is not the same for every professional at every income level — and it is not permanent. Understanding what drives the decision, at the starting income level, prevents both the cost of incorporating too early and the cost of delaying when the timing is right.

The Core Trade-Off

Sole proprietorship is simple. Income and expenses are reported on Form T2125 of the personal T1 return. No corporate registration, no separate bank account requirement, no T2 filing, no payroll setup, no annual corporate maintenance. The professional deducts business expenses against their gross professional income. All net income is personal income in the year earned.

Corporation introduces a layer of complexity but creates the deferral benefit: active income taxed at the small business corporate rate (approximately 12.2% in Ontario) rather than personal marginal rates that can exceed 53%. The income that stays in the corporation is not immediately taxed at personal rates.

The deferral benefit only exists to the extent that the professional does not need all of the income personally. A professional who draws every dollar the corporation earns — because their personal expenses require it — gains very little from the corporate structure. The administrative cost of the corporation may not be justified.

The Income Threshold

As modelled in Article 113 (contractor context), the incorporation advantage becomes clear when:

Net income exceeds approximately $100,000–$120,000, and

The professional can leave at least 30–40% of net income inside the corporation each year

Below these conditions, incorporation is often more expensive in compliance costs than it saves in tax deferral.

Above $200,000 of net income, where the professional can comfortably retain $80,000–$100,000 inside the corporation, incorporation is almost always the right structure.

The Year-One Exception

In the first year of practice, income is typically lower than subsequent years — a full-year practice was not operating from January. Many professionals begin as sole proprietors in year one simply because the income does not yet justify incorporation, then incorporate at the beginning of year two or year three when the practice is fully established and income is higher.

This staged approach has a secondary benefit: the sole proprietor's year-one expenses — home office, vehicle, professional development, software — are directly deductible on the T1 without the complexity of a corporate setup. Simplicity in year one allows the new professional to focus on building the practice.

Professional Regulatory Considerations

Some professions in Ontario can only incorporate through a professional corporation — the regulatory body restricts the share ownership and imposes specific conditions (as discussed for architects in Article 50 and physicians in Article A1). For these professions, the question is not "corporation or sole proprietor" but "professional corporation now or sole proprietor until the income justifies the regulatory compliance overhead."

The Transition Tax Issue

A professional who has operated as a sole proprietor and built up work in progress (unbilled time, uncompleted files) at the time of incorporation must handle the transition carefully. Unbilled WIP is generally not yet income until billed — but the timing of recognition around the incorporation date can create an overlap that concentrates income in the transition period.

A section 85 rollover (Article 92) may be relevant if the sole proprietor has accumulated business assets — equipment, goodwill, client lists — with significant fair market value that would otherwise be deemed disposed of at FMV at the time of incorporation.

When to Speak With a CPA

The decision to incorporate — and the timing of that decision — benefits from modelling at the professional's specific income level and personal draw requirements. A CPA can confirm the threshold at which incorporation produces a clear benefit and ensure the transition is structured correctly.

Rotaru CPA works with new professionals on the incorporation decision and the transition from sole proprietorship to corporate practice. Book a consultation to model the decision for your specific situation.