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If you work for yourself in Mississauga, an $80,000 profit costs about $13,234 for income tax and $8,893 for CPP, $22,126 together. That leaves $57,874, so 27.7% of your income goes to tax and CPP. We took “H&R Block Mississauga” to mean tax help in Mississauga from a local office. We can’t vouch for any firm, so this page covers the two things that trip up self-employed filers: paying on time and fixing a return after you’ve filed.
What does a self-employed return cost you?
Employees pay half the CPP and their employer pays the other half. When you’re self-employed you pay both halves. With an $80,000 profit in Ontario, the self-employed tax calculator gives this split.
| Item | Amount |
|---|---|
| Federal tax | $8,698.44 |
| Ontario tax | $4,535.12 |
| Income tax total | $13,233.57 |
| CPP, both halves | $8,892.90 |
| Left after both | $57,873.53 |
Two limits to know about. The tool leaves out EI. And it lets deductions lower your income tax but not your CPP, which may not match your return exactly. So use it for a planning number, not the final figure.
When do you have to pay?
For the 2025 return, self-employed people had until 15 June 2026 to file. Any balance owing was still due on 30 April 2026. Interest runs from that date, so a June filing doesn’t buy you a June payment. The CRA hasn’t published 2026 return dates yet.
Then there’s instalments. The CRA says you may have to pay them for next year if your net tax owing is more than $3,000 for 2026 and in either 2025 or 2024. The due dates are 15 March, 15 June, 15 September and 15 December. Look at your last two returns first. If you owed more than $3,000 both times, expect to pay in quarters. The tax instalments calculator splits a yearly amount into four equal payments.
What if you’ve already filed and got it wrong?
It happens. A slip turns up late, or a receipt does. You can fix it. First wait for your notice of assessment, since the CRA won’t take a change request before it. After that, send the change through “Change my return” in your CRA account, or through ReFILE in your tax software. The CRA says both take about 2 weeks. A paper T1-ADJ form sent by mail takes about 19 weeks.
You can’t change everything this way. Your address, direct deposit and marital status are handled separately. A refund can’t be issued on a change beyond 10 calendar years back. After the review you get a notice of reassessment, or a letter if the CRA turns the change down.
Is it worth paying someone in Mississauga?
Side income of a few thousand dollars? Probably not. For a business with expenses, a vehicle, GST/HST or a spouse who also earns, yes. Pick from the CRA’s list of certified preparers and ask for the fee up front. Form T183 is what you sign so they can file, and the return remains yours to answer for. Keep records at least 6 years.
We couldn’t confirm what any local business charges, so ask for two quotes and compare what each covers. A good sign is a preparer who asks for your expenses by category and not one who says they’ll “find something”.
Small habits that save you money
Open a separate bank account for the business. Set aside a slice of each payment when it lands, around the 27.7% in the example, then adjust once real costs show up. Check the marginal tax rate calculator before you buy something big for the business, since the next dollar you earn is taxed harder than the average one.
And file when you’re ready, not at the last minute. Late filing can delay benefit payments as well, which the CRA warns about.
Where the numbers come from
The example comes from our calculator, using 2026 federal, Ontario and CPP data (self-employed CPP of 11.9% up to $8,460.90 plus the second tier). Due dates, instalment rules and the change-a-return steps come from Canada Revenue Agency pages, read in September 2026. We left out any price or claim about a named firm because we couldn’t check it.
Frequently asked questions
How much tax does $80,000 of self-employed income cost in Ontario?
Our calculator shows $13,233.57 in income tax and $8,892.90 in CPP, which leaves $57,873.53. It leaves out EI and business expenses.
When was the 2025 self-employed filing deadline?
15 June 2026 to file, but any balance owing was still due on 30 April 2026.
Do I have to pay tax instalments?
The CRA says you may if your net tax owing is over $3,000 for 2026 and in either 2025 or 2024. Payments are due 15 March, 15 June, 15 September and 15 December.
How do I change a return I already filed?
Wait for your notice of assessment, then use Change my return in your CRA account or ReFILE in your software. The CRA says both take about 2 weeks.
How far back can I ask for a refund?
The CRA says a refund can't be issued on a change request beyond 10 calendar years.
- 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.