T4 Slip vs. Notice of Assessment: What's the Difference?
Two documents, two sources, one tax season – here is what each one actually means.
Written and reviewed by Rocco Clayfield, Founder & DirectorLast reviewed
Short answer
A T4 slip comes from your employer and summarises the employment income and deductions reported to the CRA on your behalf for the calendar year. A Notice of Assessment (NOA) comes from the CRA after you file your tax return and tells you whether you owe more tax, are getting a refund, or have broken even. They arrive in sequence: your T4 first, then your NOA after you file.
Every February and March, two pieces of paper tend to arrive in quick succession and cause a lot of confusion. The T4 and the Notice of Assessment are both tax documents, both relate to the same income year, yet they come from completely different sources and tell you very different things.
Knowing the difference saves time, reduces stress, and helps you catch problems early. If the numbers on your NOA do not match what you reported using your T4, that is a signal worth investigating.
What this page helps you check
- Whether your T4 employment income matches what you earned for the year
- Whether the CPP, EI, and income tax deducted on your T4 match your year-to-date pay stub totals
- Whether your NOA shows the refund or balance owing you expected
- Whether the CRA made any adjustments to your return and why
- Whether your RRSP deduction limit on the NOA looks correct
- Whether you received a T4 from every employer you worked for in the year
- Whether the name, SIN, and employer information on your T4 are accurate
What a T4 slip is
A T4 slip, formally called a Statement of Remuneration Paid, is prepared by your employer and filed with the CRA each February. You receive a copy. It shows your total employment income for the calendar year along with the amounts your employer deducted for income tax, CPP contributions, and EI premiums.
The T4 is the starting point for your personal tax return. The income in Box 14 goes onto your T1 general return. If you had more than one employer during the year, you should receive a T4 from each one.
What a Notice of Assessment is
A Notice of Assessment (NOA) is a document the CRA sends to you after it processes your tax return. It confirms what the CRA calculated as your income, the credits and deductions it accepted, and whether you owe additional tax or are entitled to a refund.
The NOA also shows your updated RRSP contribution room for the following year, any carry-forward amounts, and your account balance. It is not a tax bill in all cases; it is a statement of the CRA's assessment of your return.
The sequence: T4 first, then NOA
Employers must issue T4 slips to employees by the last day of February following the tax year. You then use that T4 to file your T1 tax return. After the CRA processes your return, it issues a Notice of Assessment. If you file early, your NOA may arrive within a few weeks; paper returns can take longer.
The NOA is always the CRA's response to your return. You cannot receive an NOA without first filing a return, and you generally cannot file accurately without your T4.
When the two documents conflict
If the income or deduction figures on your NOA do not match what you reported using your T4, the CRA may have adjusted your return. Common reasons include a reassessment based on employer-filed amounts that differ from the T4 you received, or missing income slips.
If you believe your T4 contains an error, contact your employer's payroll team first. Employers can file an amended T4 with the CRA. If the issue is with the NOA itself, you have the right to object using the CRA's formal objection process. Both processes take time, so acting promptly is worthwhile.
Protecting your documents
Keep both documents for at least six years. The CRA can reassess returns within a normal reassessment period, and in some circumstances longer. Your NOA is also frequently required as proof of income for mortgages, rental applications, and benefit programs.
In Quebec, Revenu Quebec issues its own provincial assessment in addition to the federal NOA. If you live in Quebec, you file two returns and receive two assessments.
Quebec works differently
Common red flags worth checking
These do not automatically mean there is an error. They are simply lines worth a closer look, or worth asking payroll to explain.
Your T4 shows income significantly higher or lower than your total gross pay
Compare Box 14 on your T4 against the year-to-date gross on your final pay stub for the year. A large discrepancy could mean a taxable benefit or other income was added, or that a pay period was missed. Ask payroll to explain any difference.
Your NOA shows a large unexpected balance owing
If you expected a refund and received a large bill, the CRA may have disallowed a deduction or included additional income. Review the attached explanation on your NOA and contact the CRA or a tax professional if the reason is not clear.
You received a T4 from an employer you no longer work for with incorrect amounts
Former employers are still required to issue accurate T4 slips. If the amounts are wrong, contact the employer's payroll or HR department to request a corrected T4 (T4 amendment). Filing with an incorrect T4 can lead to a reassessment.
Tax withheld on your T4 is much lower than expected
If you did not update your TD1 forms after a significant income change, your employer may have withheld too little tax. This can result in a balance owing at tax time. It does not necessarily mean an error was made, but reviewing your withholding going forward is worth doing.
Your NOA RRSP room looks much lower than you expected
RRSP room is calculated based on your earned income from prior years. If the figure seems low, check whether all your income sources were reported correctly. Pension adjustments from employer plans also reduce RRSP room and appear in Box 52 of your T4.
You never received a T4 by the end of February
If you worked for an employer during the year and have not received a T4 by the end of February, follow up with your employer. If you cannot obtain it, the CRA has a process to help you estimate and file without it, and you can access slip information through My Account on the CRA website.
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What to ask payroll or HR
Calm, specific questions get clearer answers. You can copy any of these, or build a full message with the Payroll Message Generator.
- “Can you explain why Box 14 on my T4 is different from my year-to-date gross pay on my final stub?”
- “Is there a taxable benefit included in my T4 employment income that does not appear as a cash pay line on my stubs?”
- “My T4 shows a different income tax withheld than my year-to-date deduction total. Can you reconcile that?”
- “I believe there is an error on my T4. What is the process to request a corrected slip from the employer?”
- “My year-to-date CPP contributions on my T4 do not match my stubs. Can you check whether any corrections were made after the year ended?”
- “I worked for this company for only part of the year. Can you confirm the T4 only covers the period I was employed here?”
Frequently asked questions
When should I receive my T4?
Employers are required to provide T4 slips to employees by the last day of February following the calendar year end. If you consented to electronic delivery, your T4 will be available through your employer's payroll portal by that date.
Can I file my taxes before I receive my T4?
You can log in to My Account on the CRA website and view slips that employers have already filed. If the slip is available there, you can use those figures. Filing without the correct figures can lead to a reassessment, so it is generally better to wait unless you are close to a filing deadline.
What if my T4 has the wrong SIN or name?
Contact your employer's payroll department immediately. Errors in identifying information need to be corrected on the T4 before or shortly after filing. Your employer submits an amended T4 to the CRA, and you may need to file or refile your return once the correction is in place.
Does a Notice of Assessment mean I am being audited?
No. Every filed return generates an NOA. It is a routine confirmation, not an audit notice. An audit is a separate, more detailed review of specific items in your return. The NOA will clearly indicate if the CRA has questions or is requesting more information.
My NOA shows a different refund amount than I calculated. What do I do?
Review the explanation section of your NOA to see what the CRA changed. Common adjustments include corrected income amounts, changed deductions, or benefit calculations. If you disagree, you can file a notice of objection within the time limit stated on the NOA.
How long should I keep my T4 and NOA?
The CRA recommends keeping supporting documents for at least six years from the end of the tax year they relate to. Some situations, such as capital losses or RRSP contribution history, may warrant keeping records longer.
I have multiple T4s. Do I add the income together?
Yes. All employment income from all T4 slips for the year is combined on your T1 return. The CRA totals your income from all sources, so missing a T4 can result in a reassessment.
What is the RRSP deduction limit shown on my NOA?
The RRSP deduction limit (also called RRSP room or contribution room) is the maximum you can contribute to your RRSP in the coming year. It is based on your earned income from the prior year, minus any pension adjustment. The CRA calculates and displays this figure on your NOA each year.
Official sources for this page
Every figure here is derived from these. Where a number matters to you, read it at the source — PayStub IQ Canada explains the rules, it does not set them.
- Understanding your notice of assessment — Canada Revenue Agency
- Understanding your T4 slip — Canada Revenue Agency
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Helpful guidance, not advice
PayStub IQ Canada provides educational payroll explanations based on the information visible in your document. It does not provide legal, tax, accounting, payroll, CRA, Revenu Québec, or employment standards advice. For official decisions or corrections, contact your employer, payroll department, CRA, Revenu Québec, your provincial or territorial employment standards office, or a qualified professional.