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Taxes in Oshawa work like taxes anywhere in Ontario: one return, one deadline, a pile of slips. For the 2025 return the deadline was 30 April 2026, and the CRA hasn’t published dates for the 2026 return yet. We assumed you’re looking for a tax office in Oshawa. We can’t vouch for any local business, so this page is the checklist you’d want in hand before you see one, plus what Ontario adds to the bill.
What do you need for taxes in Oshawa?
The CRA’s list is short. You need your tax slips (T4 from each employer, T4A and the rest), receipts for anything you’ll claim, and your most recent notice of assessment. That notice carries the 8-character access code some filing methods use. If your address, marital status or direct deposit changed, tell the CRA before you file.
- Every T4, T4A, T5 and T3 slip
- RRSP and FHSA contribution receipts
- Receipts for medical costs, donations and child care
- Rent or property tax amounts, if you’ll claim Ontario benefits
- Last year’s notice of assessment
Slips can arrive late, so don’t file the day your first one shows up. Look in your CRA account to see which ones it already holds. A missing slip is still yours to report.
What does Ontario add to your tax?
Besides the Ontario tax rates and a surtax at higher incomes, there’s the Ontario Health Premium. It’s a charge on your return that rises with taxable income, and it’s why Ontario tax jumps in narrow bands near $72,000 and $200,000. Here’s how our calculator applies it.
| Taxable income | Health premium |
|---|---|
| Up to $20,000 | $0 |
| $20,000 to $36,000 | 6% of the excess, up to $300 |
| $36,000 to $48,000 | Up to $450 |
| $48,000 to $72,000 | Up to $600 |
| $72,000 to $200,000 | Up to $750 |
| Over $200,000 | Up to $900 |
The premium is why the marginal tax rate calculator shows a very high rate at those points. It’s a real feature of the tax, not a glitch, though only for a few hundred dollars of income at a time.
Is there Ontario money to claim on the return?
Yes, possibly. The Ontario Trillium Benefit is paid through the return, in three parts: the Ontario Sales Tax Credit, the Ontario Energy and Property Tax Credit and the Northern Ontario Energy Credit. You apply by filing and completing Form ON-BEN. The CRA says the sales tax credit needs no application, since it uses your 2025 return. You must file even with no income. If you file late you still get the benefit, but the payments may be delayed.
We haven’t listed benefit amounts here, because they depend on income, rent or property tax and family. The CRA’s Ontario Trillium Benefit page has them, and the GST/HST credit calculator covers the federal credit that’s paid on the same filing.
A worked example for an Ontario employee
Say you earned $70,000 at one job and $9,000 of tax was withheld. The tax refund calculator gives tax of $11,133.91 on taxable income of $69,335. That leaves $2,133.91 to pay. Not a refund, and it surprises people whose pay stub looked fine. Someone with $100,000 and $20,000 withheld ends up close to even, owing $24.35.
Taxable income is lower than pay because the calculator deducts the extra slice of your CPP contributions. That’s about 1% of pay above $3,500.
Paid preparer or do it yourself?
One T4 and an RRSP receipt? Do it yourself in software. Rental income, a business, a move or old unfiled years? Then a certified preparer is worth a look. The CRA keeps a directory. Get the fee in writing, and read the return before you sign the T183. The numbers stay your responsibility.
If you’re self-employed, you have until 15 June to file the 2025 return, but the tax still had to be paid by 30 April. Estimate it with the self-employed tax calculator, which leaves out EI.
Where the numbers come from
Filing dates and the document list come from the Canada Revenue Agency pages on the 2025 return and on getting ready to file. The Ontario Trillium Benefit details are from the CRA page on that benefit. Tax and premium figures come from our 2026 tax data. We couldn’t confirm any fee or service of a local firm.
Frequently asked questions
What do I need to file my taxes in Ontario?
Your slips such as the T4, receipts for claims, and your latest notice of assessment. Update your address and direct deposit with the CRA first.
What is the Ontario Health Premium?
A charge on your Ontario return that rises with taxable income, from $0 up to $900 in our calculator.
How do I get the Ontario Trillium Benefit?
File your return and complete Form ON-BEN. You must file even with no income, and the sales tax credit needs no application.
When was the deadline for the 2025 return?
30 April 2026 for most people, and 15 June 2026 to file if you or your spouse are self-employed, with payment still due 30 April.
Do I need a tax preparer in Oshawa?
Not for a simple return. If you use one, pick from the CRA directory of certified preparers, get the fee in writing and review the return before you sign.
- How Canadian income tax works: brackets and credits
How federal and provincial Canadian income tax stack up, what marginal and average rates mean, and how credits and deductions change your bill
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.