Common Personal Tax Filing Mistakes Canadians Make
(and How to Avoid Them)
Taxation

Tax season is in full swing, and while filing your return might feel routine, even small errors can lead to delays, reassessments, or unwanted letters from the CRA.

The truth? Most tax mistakes aren’t dramatic; they’re simple oversights. A missing slip. A miscalculated credit. A box left unchecked.

Let’s walk through the most common personal tax filing mistakes Canadians make — and how you can avoid them in 2026.

1. Forgetting to Report All Income

This is one of the most frequent triggers for CRA reassessments.

Commonly missed income includes:

• T5 investment income
• Side hustle or freelance earnings
• Rental income
• Gig economy earnings (Uber, DoorDash, etc.)
• Foreign income
• Cryptocurrency transactions

The CRA receives copies of most slips directly. If you leave something off, their system usually catches it.

Avoid it:
Log into CRA My Account before filing and confirm that all issued slips match your return.

2. Incorrectly Reporting Capital Gains

If you sold:

• Stocks
• ETFs or mutual funds
• Cryptocurrency
• Rental or secondary property

You must report capital gains (or losses) accurately.

Common errors include:

• Using incorrect purchase prices
• Ignoring transaction fees
• Forgetting to adjust the cost base for reinvested dividends
• Failing to report principal residence sales

Even if your property qualifies for the principal residence exemption, it still must be reported.

Avoid it:
Keep detailed records of purchase dates, prices, and improvements. Don’t rely on memory.

3. Claiming Ineligible Home Office Expenses

Since remote work became more common, home office claims have increased — and so has CRA scrutiny.

Mistakes include:

• Claiming personal living space
• Overestimating square footage
• Claiming expenses without receipts
• Not meeting eligibility requirements

Avoid it:
Ensure the workspace is used primarily for work and calculate the percentage accurately.

4. Missing Valuable Tax Credits

On the flip side, some taxpayers leave money on the table by forgetting credits such as:

• Medical expenses
• Charitable donations
• Tuition transfers
• Canada Workers Benefit
• Disability tax credit
• Childcare expenses

Small credits add up quickly.

Avoid it:
Review last year’s return — if you claimed something before, double-check eligibility again.

5. RRSP Contribution Confusion

A common mistake involves reporting RRSP contributions incorrectly.

Issues include:

• Claiming contributions twice
• Forgetting contributions made in the first 60 days of 2026
• Exceeding contribution room

Your Notice of Assessment lists your available RRSP room. Always confirm before claiming.

6. Ignoring Instalment Requirements

If you owed more than $3,000 in tax in 2025, you may be required to pay instalments in 2026.

Many taxpayers overlook CRA instalment notices — which can result in interest charges.

Avoid it:
Review your Notice of Assessment carefully and set reminders for March, June, September, and December if required.

7. Filing Late (Even If You Can’t Pay)

Some taxpayers delay filing because they can’t afford to pay the full balance owing.

This makes things worse.

Late filing penalties are immediate and are 5% of the balance owing.

Interest compounds daily.

Avoid it:
File on time, even if you can’t pay immediately. You can arrange a payment plan with the CRA.

8. Not Reviewing Before Submitting

Tax software makes filing easier — but it doesn’t replace review.

Simple typos in:

• SIN numbers
• Banking information
• Marital status
• Dependant details

can delay refunds significantly.

Take five extra minutes. It’s worth it.

💡 Related Reading:

• How to Prepare for Personal Tax Season in Canada (Without the Stress)
• What the CRA Is Watching More Closely in 2026

Final Word

Tax filing mistakes are common — but preventable. A little preparation, careful review, and early action can save you time, money, and stress.

If your return involves investments, rental income, business earnings, or major life changes, professional guidance can make all the difference.

Because in tax season, accuracy isn’t optional — it’s essential.

The information in this article is general in nature. We recommend that you discuss your situation with an advisor as everyone’s situation is unique.