Missing a T4 slip on your tax return is more common than you might think — especially if you had multiple jobs, worked briefly for an employer, or changed jobs mid-year. The important thing to understand is that CRA already has your T4 information, so it’s not a matter of whether they’ll find out, but when.
Why CRA Already Knows About Your Missing T4
Every employer in Canada must file T4 slips with CRA by the last day of February following the tax year. CRA’s systems automatically match employer-reported T4 data against your filed return. If your return is missing income, CRA will flag it.
This matching process typically happens a few months after the April 30th filing deadline, so many people receive reassessments in late summer or fall.
What Happens If CRA Finds It First
If you don’t correct the error yourself, CRA will issue a Notice of Reassessment that:
- Adds the missing income to your taxable income
- Recalculates your tax owing based on the revised amount
- Charges arrears interest from April 30th of the filing year at CRA’s prescribed rate (currently approximately 8–9% annually, compounded daily)
- May reduce any refund you received or create a new balance owing
Important: If you already received a refund that was too large because of the missing T4, you’ll have to pay it back plus interest.
Late Filing Penalties (If the Return Was Never Filed)
If you haven’t filed the tax year at all (not just missed a slip), late filing penalties are steeper:
| Scenario | Penalty |
|---|---|
| First offence | 5% of balance owing + 1%/month (max 12 months) |
| Second offence within 3 years | 10% of balance owing + 2%/month (max 20 months) |
| CRA demanded the return (TX11 letter) | Minimum $100 penalty |
Filing late — even if you can’t pay — stops the penalty from growing. If you owe money, pay what you can and contact CRA to set up a payment arrangement.
How to Fix a Missing T4 Yourself
If you haven’t filed yet
Simply include all T4 slips in your return. Report employment income on line 10100 and income tax withheld on line 43700 for each T4.
If you’ve already filed
Step 1: Locate the T4
- Log in to CRA My Account → Tax information → Tax slips. CRA posts the T4 data provided by your employer.
- Contact your employer’s payroll department if you need the actual slip.
Step 2: Submit a T1 Adjustment
Online (fastest — 2 weeks): In CRA My Account, go to “Change my return” → select the tax year → update line 10100 (employment income) and line 43700 (income tax deducted). The system will recalculate automatically.
By mail (8–12 weeks): Complete Form T1-ADJ with the corrected line amounts and attach a copy of the T4 slip. Mail to your tax centre.
Step 3: Pay any balance owing promptly Once CRA reassesses your return, pay any outstanding balance immediately to stop interest from accruing further. You can pay via:
- CRA My Account → Make a payment
- Online banking (CRA is a payee at most Canadian banks)
- In person at a Canada Post outlet
What If Your Employer Made the Error?
If your employer failed to include CPP contributions, EI premiums, or income tax on the T4, or reported an incorrect amount, contact your employer first. If they won’t correct it, file a complaint with the Canada Revenue Agency. Employees are not penalized for their employer’s T4 errors when corrected properly.
Using the Voluntary Disclosures Program
If you have multiple unfiled years or a pattern of unreported income that goes beyond a simple slip, you may qualify for CRA’s Voluntary Disclosures Program (VDP). VDP allows you to come forward voluntarily and potentially have penalties and some interest waived. A tax professional can help assess whether VDP is appropriate for your situation.