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To file income tax online in Canada you need certified tax software, your slips and a NETFILE access code from your CRA account. For the 2025 return the deadline was April 30, 2026, and the CRA’s e-file services stay open until January 29, 2027, so a late return can still go in online.
What do you need before you start?
Less than you’d think.
At tax time, gather your slips first, because most of them (T4s, T5s and the like) are issued by the end of February. Then you need the software itself, and an access code if you’re using NETFILE.
The code is eight characters, letters and numbers. Since February 2026 the CRA shows it in your CRA account under your tax returns, so you don’t have to dig through last year’s notice of assessment. Your social insurance number and date of birth are the other two things the software will ask for.
Is your software allowed? The CRA keeps a list of certified products for each tax year, on its tax software for filing personal taxes page. If a program isn’t on it, the CRA won’t accept what it produces.
Which dates matter for the 2025 return?
| Item | Date (2025 return) |
|---|---|
| Online filing opened | February 23, 2026 |
| File and pay, most people | April 30, 2026 |
| File, self-employed with business expenses | June 15, 2026 |
| Pay any balance, self-employed | April 30, 2026 |
| Last day for e-file services this cycle | January 29, 2027 |
The 2026 return dates aren’t on a CRA page yet, so don’t assume they match. Check the CRA’s important dates page in early 2027.
One trap here. The June 15 date only moves the filing deadline. If you owe tax, interest still starts after April 30.
How do you file income tax online, step by step?
Pick a certified product and enter your details. Most programs ask about your year in plain questions, then fill the right boxes for you. If you’ve filed before, many can pull last year’s answers.
Then enter your slips by hand, or let the software fetch them if it offers that. Check the numbers against the paper or PDF slip. A typo in box 14 of a T4 changes everything below it.
Before you send, look at the result. A refund of $1,295 on $75,000 of pay with $14,000 withheld in Ontario is what our tax refund calculator shows, and that’s roughly the scale you’d expect. If your software says $9,000 instead, something was entered wrong.
Send it.
Then save the confirmation number. You’ll want it if the CRA ever questions a filing date.
What happens after you hit send?
The software tells you the return was received, and that’s the number to screenshot or print. A notice of assessment follows later, and it’s worth reading properly instead of filing it away. Compare its refund or balance to what your software showed. If the two are far apart, the CRA changed something, and the notice says what.
Keep a copy of the return and your slips somewhere you can find them in a hurry. Maya in Halifax, say, gets a letter two years later asking about a tuition claim. She’ll be glad she saved the PDF.
Can you file an old return online?
Yes, within limits. The same CRA page lets you send returns for 2018 to 2025 through NETFILE until January 29, 2027, as long as your software offers those years. For anything older than 2018, check the CRA’s instructions instead of guessing.
If you’re catching up on several years, do the oldest first. Credits and carry-forward amounts, such as unused tuition, flow from one year to the next.
Is there a free way to file?
For simple returns, yes. The CRA points lower-income people with simple situations to free tax clinics and to its SimpleFile services, which opened on March 9, 2026. We didn’t confirm the income limits for those services, so read the CRA page before you rely on one. Private software often has a free tier as well, but what it includes changes from year to year, and we didn’t verify any of it.
The practical test is simple. Ask whether the free version covers every slip you have, including self-employment income. Many free tiers stop there.
What goes wrong when people file online?
Most errors are small and avoidable.
- Mixing up the access code with your CRA account password.
- Forgetting a slip that arrives in March, such as a T5 from a brokerage.
- Entering the wrong bank details, which sends your refund to the wrong place or delays it.
- Skipping the deductions you can claim, like RRSP contributions.
The last one costs real money. On $75,000 of pay, a $5,000 RRSP deduction lifts that estimated refund from about $1,295 to about $2,928. You can test your own numbers with the income tax calculator, and the tax credits calculator shows the federal credits you may be missing.
And if you work for yourself, the filing is only half of it. Instalments may be due through the year, which the tax instalments calculator can size up for you.
Where this information comes from
Dates and the NETFILE details come from the Canada Revenue Agency‘s pages for the 2025 tax year, read on September 30, 2026. The refund figures come from our own calculators, which use 2026 federal and Ontario rates, so they’re estimates and won’t match a 2025 return to the dollar. No government body has reviewed or endorsed what you read here.
Frequently asked questions
Do I need a NETFILE access code?
Yes, if you use NETFILE. It has eight characters and is shown in your CRA account under your tax returns.
Can I file an old return online?
The CRA says NETFILE takes initial returns for 2018 through 2025. Check that your software still supports the year you need.
When is the deadline for the 2025 return?
April 30, 2026 for most people, and June 15, 2026 if you or your spouse were self-employed. Any balance owing was still due April 30.
Is online filing free?
The CRA offers free clinics and SimpleFile for simple returns. Private programs price their own versions, and we didn't verify those.
What if I file late?
Interest and penalties can apply to a late return with a balance owing. File anyway, because a late return also delays benefits.
- How to file your tax return in Canada: steps and dates
What to gather, when your return is due and how to file in Canada, from the first slip to the notice of assessment that closes the year