Missing a T4 is one of the most common filing errors — it happens most often when you had two jobs, left an employer mid-year, did seasonal or contract work, or simply misfiled a slip before April. The good news: the fix is straightforward, and the CRA expects this to happen.
Why you need to act before the CRA finds it
Every employer is required to submit T4 slips to the CRA by the last day of February. The CRA’s systems match those slips to filed returns each spring. If your return does not include income from a T4 on file, expect a Notice of Reassessment adding the missing employment income, additional tax owing, and prescribed interest from April 30. Filing a T1 Adjustment yourself first is faster and avoids any civil penalty risk.
Step 1: Find the missing T4
CRA My Account (easiest)
- Log in to CRA My Account
- Go to Tax Information Slips and select the tax year
- All T4s on file — including from employers you may have forgotten — are listed here
Contact the employer If you no longer have the original slip, contact the employer’s payroll department and ask for a reissue. They are required to provide one. For employers you cannot reach (e.g., a business that has closed), the CRA can help — call 1-800-959-8281.
Use your final pay stub If you need to file before obtaining the actual T4, use your December pay stub. Box 14 on the T4 (employment income) will match your year-to-date earnings on your last stub. How to read your pay stub explains the key boxes.
Step 2: File a T1 Adjustment
Once you have the T4 in hand, amend your return to add the missing income.
CRA My Account — Change My Return (~2 weeks)
- Log in to CRA My Account and select Change My Return
- Choose the tax year
- Update Line 10100 (employment income) with the full corrected total
- If the T4 includes CPP contributions (Box 16) or EI premiums (Box 18) you had not claimed, update those lines too
- Submit with a brief explanation: “Adding T4 from [Employer Name] not included in original filing”
Tax software amendment (2–3 weeks)
Open your prior-year return, add the T4 in the income section, and re-NETFILE the amendment.
Mail T1-ADJ form (6–8 weeks)
Complete the T1-ADJ form, attach a copy of the T4, and mail to your CRA tax centre.
What you will likely owe
Adding a forgotten T4 almost always means you owe more tax. The additional amount depends on:
- The employment income on the T4 — taxed at your marginal rate
- CPP and EI contributions — if your other employer did not max them out, you may owe additional employee contributions (or get a refund if you over-contributed across two employers)
- Interest — the CRA charges prescribed interest from April 30 on any additional tax balance
One bright side: if both employers withheld CPP and EI independently, you may have over-contributed across the two jobs. The excess CPP and EI contributions are refundable — the T1 Adjustment should pick this up automatically.
If you had two employers who both withheld income tax
Two T4s do not always mean you under-withheld. If each employer withheld based on your income with them alone — common for part-time or seasonal work — neither may have known about the other job, and both withheld at a low rate. The combined income could push you into a higher bracket, meaning you owe more at tax time. This is one of the most common reasons for an unexpected tax bill, and adding the second T4 to your return corrects it properly.
Filing on time when a T4 is missing
If the April 30 deadline is approaching and you still do not have the T4, file on time using your best estimate. Use your last pay stub or any documentation you have. The CRA prefers an on-time return with a minor error over a late return — late filing when you owe triggers a 5% penalty immediately plus 1% per month. Once the T4 arrives, file a T1 Adjustment to correct the figures.
See what to do if you made a mistake on your tax return for the full amendment process, and the T4 slip explained if you need help reading the boxes.