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A business tax accountant earns their fee when the tax bill is big enough to plan around. On $100,000 of active business income, an Ontario corporation owes about $11,696 in 2026 by our corporate tax calculator. The accountant’s job is to make sure that number is right, filed on time, and not a surprise.
What does a business tax accountant actually do?
The work splits into a few pieces. They prepare your return, whether that’s the T1 for a sole proprietor or the T2 for a corporation. They keep track of GST/HST and payroll remittances, and they tell you when your structure has stopped fitting your income.
The last one matters most. Nobody needs an accountant to tell them what the return form says. You need one when someone has to decide if you should stay a sole proprietor, incorporate, pay yourself in salary or take dividends. Those choices change the bill by thousands.
Do you need one at all? If you’re a freelancer with a few clients, simple expenses and no employees, probably not every year. Software can handle that. Once you hire staff, register a corporation, or own more than one business, the answer flips.
Which deadlines will they be watching?
These are the 2026 dates the CRA publishes for businesses. Weekend and holiday dates move to the next business day.
| Who | What is due | Date |
|---|---|---|
| Self-employed person | Return filed | June 15, 2026 |
| Self-employed person | Tax owing paid | April 30, 2026 |
| Self-employed person | Instalments | March 15, June 15, September 15, December 15 |
| Employer | T4 slips | Last day of February |
| Corporation | T2 return | Six months after year end |
| Corporation | Balance owing | Two months after year end, three for many small Canadian-controlled private corporations |
The gap between filing and paying trips up a lot of sole proprietors. You get until June 15 to file, but interest starts running on April 30. If you owe, the tax instalments calculator shows what four equal payments would look like.
Is a corporation really cheaper than a sole proprietorship?
Sometimes, on paper. But the comparison is easy to get wrong, so here are two numbers from the calculators, with a warning attached.
A sole proprietor in Ontario with $90,000 of net income owes $16,079.97 in income tax and $9,292.90 in CPP, according to the self-employed tax calculator. That leaves $64,627.13. An Ontario corporation earning $100,000 pays $11,696, leaving $88,304 inside the company.
That $88,304 isn’t in your pocket yet. Taking it out as salary or dividends triggers a second layer of personal tax, and the corporate figure doesn’t include it. The dividend tax calculator covers the dividend side. Whether incorporating wins depends on how much you need to spend personally each year. If you’d take out nearly all of it, the gap shrinks fast.
One more caveat on the corporate figure. Ontario cut its small business rate on July 1, 2026, so a calendar 2026 year gets a prorated blend. We derived that blend by days, and the province doesn’t publish it. Ask your accountant for the exact rate for your year end.
What should you ask before you hire?
Start with the licence. In Ontario, the CPA Ontario directories let you look up a member, a firm or a public accounting licence holder in a couple of minutes. Other provinces have their own bodies.
Then ask how they’d handle your situation, not how good they are in general. Have they filed for businesses your size and type? Who watches the dates? What does the quote cover? Bookkeeping, payroll and GST/HST filing are often priced apart, so a low quote can mean fewer services.
We couldn’t confirm typical fees from an official source, so we won’t quote any. Get two written quotes and compare what each one includes.
What mistakes cost owners the most?
Mixing personal and business spending is the classic. It makes the books harder to trust and the year end slower and dearer. Waiting until April to call is the second. By then most planning choices for the year are gone.
Ignoring payroll is the third. Every employee means remittances on a schedule. For one employee paid $3,000 every two weeks in Ontario, the payroll remittance calculator puts the amount to send at $961.03 a pay period, and the full cost of that employee at $3,228.41.
These figures are estimates for a standard case. They leave out credits, associated companies, taxable capital and passive income rules, so your accountant’s number may differ.
Where the numbers come from
Deadlines come from the Canada Revenue Agency’s 2026 tax deadlines page for businesses and the self-employed. Federal corporate rates (15% general, 9% on the first $500,000 for qualifying small corporations) come from CRA corporate rate pages, and provincial rates from CRA and provincial sources as of September 2026. CPP and income tax figures come from 2026 CRA and Ontario data.
Frequently asked questions
When does a business tax accountant pay for itself?
Usually when you hire staff, incorporate, or run more than one business. A freelancer with simple expenses can often manage with software.
How do I check that an accountant is licensed?
Use your provincial accounting body's public directory. In Ontario, CPA Ontario lists members, firms and public accounting licence holders.
When is a self-employed return due in 2026?
June 15, 2026. Any tax owing was still due April 30, 2026, and interest runs from that date.
Is a corporation always cheaper than being a sole proprietor?
No. Money left inside the company is taxed again when you take it out, so the saving depends on how much you spend personally.
What does a corporation owe and when?
A T2 return is due six months after year end. The balance is due two months after year end, or three for many small Canadian-controlled private corporations.
- How to choose a tax preparer in Canada
How to decide if you need a tax preparer, what a preparer does, the questions to ask before you hire one and where to find free help in Canada
Information only. This page is general information, not tax, legal or accounting advice. Tax-Services.ca is an independent publisher: we don't prepare or file tax returns or offer tax services, and we have no connection with the CRA, Revenu Québec, any government or any company named on this page. Check the figures that matter with an official source or a qualified professional.