Updated Checked by the Tax-Services.ca editorial team How we check
Taxes in Oshawa work like the rest of Ontario: one T1 return, with Ontario tax and the Ontario Health Premium worked out on it. The 2025 return was due April 30, 2026, and the usual date for the 2026 return is April 30, 2027, though the CRA has not printed it. This page is a checklist, not a firm.
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 rises with taxable income, and it’s why Ontario tax jumps in narrow bands near $72,000 and $200,000. Ontario’s health premium page (read in November 2026) says it runs from $0 at $20,000 of taxable income or less to $900 above $200,600, and that your employer or pension provider usually deducts it from your pay. If that doesn’t happen, you pay it when you file. 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. The CRA’s Ontario Trillium Benefit questions and answers says you apply for the energy and property tax credit and the northern credit by completing the right parts of Form ON-BEN on your return, while the sales tax credit needs no application. You must file every year to keep receiving it, 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.
What if you owe money on the return?
A balance owing doesn’t wait for the paper work to settle. The CRA charges compound daily interest on unpaid tax from the day after the due date, which for the 2025 return was 1 May 2026 and for the 2026 return is 1 May 2027. If you owed $2,133.91 like our example, that’s a bill worth setting aside a few bucks a week for next year, or asking your employer about extra withholding. Employment income with a second job or a side gig is the usual culprit.
Paid preparer or do it yourself?
One T4 and an RRSP receipt? Do it yourself in free tax 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 2027 to file the 2026 return (it was 15 June 2026 for 2025), but the tax is still due 30 April 2027. 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, read again in November 2026. 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 and T5, receipts for anything you plan to claim, and your most recent notice of assessment. Update your address, marital status and direct deposit with the CRA before you file. Look in your CRA account to see which slips it already holds, because a slip that arrives late is still yours to report.
How do I get the Ontario Trillium Benefit?
File your return and complete the right parts of Form ON-BEN. The energy and property tax credit and the northern credit need that form, while the sales tax credit needs no application. You must file every year to keep receiving the benefit, even with no income, and filing late only delays the payments.
What is the Ontario Health Premium?
A premium on taxable income that runs from $0 at $20,000 or less to up to $900 above $200,600, according to Ontario. Your employer or pension provider usually deducts it from pay. If nobody does, you pay it when you file. It is why the marginal rate jumps in narrow bands near $72,000 and $200,000.
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 Form T183. For rental income, a business, a move or old unfiled years, a certified preparer is worth a look. You stay responsible for the numbers.
When is the balance owing due?
April 30. For the 2025 return that was April 30, 2026, and for the 2026 return the usual date is April 30, 2027. Interest on unpaid tax starts the day after. Self-employed people have until June 15 to file, which is June 15, 2027 for the 2026 return, but the tax is still due April 30.
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