What is a CRA Notice of Reassessment?

A Notice of Reassessment (NORA) is CRA's formal notification that it has reviewed and changed a previously assessed tax return. When you first file, CRA sends a Notice of Assessment (NOA). If CRA later reviews that return and finds changes — either in your favour or resulting in additional tax owing — they send a Notice of Reassessment with the updated amounts. The NORA shows: the changed line items; the difference from the original assessment; any new balance owing or refund; the deadline to object if you disagree. CRA can reassess within 3 years of the original assessment date for most individuals (longer if fraud or misrepresentation is alleged).

What triggers a CRA tax reassessment?

CRA reassessments are triggered by several common causes: (1) Third-party information slips that did not match your return — T4, T4A, T5, T3, T5008 slips filed by employers, banks, or investment firms are compared to your return. Any mismatches flag an automatic review. (2) T1 Adjustment requested by you — if you filed a T1-ADJ (Amendment) to correct an error in your own return, CRA processes it as a reassessment. (3) Random or risk-based audit selection — CRA selects some returns for review based on statistical models that identify unusual claims (high expense ratios, large self-employment losses, large donation claims). (4) Related party reviews — if your spouse, family member, business partner, or employer is audited, CRA may cascade to your return. (5) Prior-year program reviews — CRA runs batch matching programs that may catch slip mismatches years after the original filing.

Does a reassessment always mean I owe money?

No. A reassessment can result in three outcomes: (1) Additional tax owing — CRA determined you under-reported income, over-claimed deductions, or missed eligible income inclusion. (2) Additional refund — CRA determined you are owed more than originally assessed, e.g., if you missed a credit or claim was under-calculated. (3) No change to amount — a review concluded with no financial difference (informational reassessment only). Most taxpayers who receive a reassessment do face additional tax owing, but reassessments also flow from T1-ADJ requests made in the taxpayer's own favour.

What should I do when I receive a Notice of Reassessment?

Step 1: Read the reassessment carefully and identify which line(s) changed and why. The NORA will typically reference the specific income, deduction, or credit that was adjusted. Step 2: Compare to your records — do you have T4/T5/T3 slips, receipts, or documentation that supports your original claim? Step 3: If you agree with the reassessment, pay any balance owing by the due date to stop interest from accruing (currently CRA charges prescribed rate + 2% on unpaid balances). Step 4: If you disagree, you have 90 days from the date of the NORA to file a Notice of Objection (Form T400A) through CRA My Account or by mail. Do not miss this 90-day deadline — late objections are typically denied.

How do I dispute a CRA reassessment I disagree with?

To dispute a reassessment: (1) File a Notice of Objection (Form T400A) within 90 days of the NORA date. You can do this online through CRA My Account → "Register a Formal Dispute" or mail the T400A form to your Tax Services Office. (2) Include: your SIN, the tax year in question, the specific items you are disputing, and your supporting documentation. (3) CRA's Appeals Branch reviews objections independently from the Audit branch. The review typically takes 6–18 months. (4) If your objection is denied, you have 90 days to appeal to the Tax Court of Canada (informal or general procedure depending on amount). Keep all documentation — receipts, contracts, bank statements — organized for the full objection and appeal process.

How far back can CRA reassess my taxes?

For most individual tax filers: CRA can reassess within 3 years of the date of the original Notice of Assessment (the "normal reassessment period"). There are exceptions: (1) If fraud or misrepresentation is alleged — no time limit; CRA can reassess any year. (2) For business income (T2125 filers) or certain investment income — extended to 4 years in some circumstances. (3) For foreign reporting failures (T1135 foreign asset reporting) — extended to 6 years from filing. Practically: keep your supporting documents (T-slips, receipts for deductions, investment records) for at least 7 years from the relevant tax year, even though the normal reassessment window is 3 years.

Can I be reassessed while I am waiting for my original assessment?

No — a reassessment requires a prior assessment. CRA must first issue a Notice of Assessment for your return before it can reassess. The timeline is: you file your return → CRA issues a Notice of Assessment (usually 2–8 weeks for NETFILE) → the 3-year reassessment clock begins on the NOA date. If CRA has not yet processed your return (no NOA issued), any changes CRA makes are technically part of the original assessment, not a reassessment. If you are waiting months with no NOA and no communication, you can check the status at canada.ca or call 1-800-959-8281.

Why Did CRA Reassess My Taxes? What Triggers a Reassessment in Canada

A Notice of Reassessment is not a crisis — but it demands attention. Most are resolved quickly once you understand what CRA changed and why.

How a reassessment is different from an audit

	Notice of Reassessment	Full Audit
Trigger	Specific slip mismatch or data discrepancy	Broader review of your return
Scope	Usually one or two line items	All items or specific topic (e.g., all business expenses)
Process	CRA makes change; you can object	CRA requests documents; you respond
Common outcome	Balance owing or refund adjustment	Similar outcome, but via different process
Time to resolve	Weeks to months	Months to over a year

Top triggers: the most common reassessment causes

1. T-slip mismatches (most common)

CRA receives your T4, T5, T3, and T5008 slips directly from your employer, bank, and investment firm. These are cross-matched to your return. Common mismatches:

Slip	What CRA checks
T4	Employment income matches Box 14 on your return
T5	Dividend and interest income matches investment income
T3	Trust income (mutual funds, ETFs) reported correctly
T5008	Proceeds of disposition match capital gains reported
T4A	Contract payments, pension income, CERB/CRB reported

2. One-time large claims

Unusually large claims relative to your income level can trigger review:

Charitable donations above 75% of net income
Home office expenses disproportionately large versus employment income
Business losses claimed for multiple consecutive years
Large medical expense claims without supporting receipts

3. T1-ADJ you filed yourself

If you submitted a T1 amendment to add a missed RRSP deduction, child care expense, or other credit, CRA processes this as a reassessment. It typically takes 8–12 weeks and may generate an additional refund if approved.

What happens if you owe after a reassessment

CRA charges interest on reassessment balances from:

The original April 30 filing deadline of the tax year in question — not from the date of the reassessment notice

This means interest can already be substantial when you receive the NORA. For example: if CRA reassesses your 2022 return in 2026 for $4,000 of additional income, interest at the prescribed rate (~8–10% annually) has been accumulating since May 1, 2023 — potentially adding $1,200+ to the amount owing before you even open the letter.

Reducing interest exposure: Pay the balance owing as soon as you receive the NORA, even if you plan to object. If your objection succeeds, CRA will refund the payment with interest.

The objection timeline

Step	Deadline
File Notice of Objection	90 days from NORA date
CRA Appeals decision	Approximately 6–18 months
Appeal to Tax Court	90 days from Appeals decision
Tax Court (informal, under $25K)	Hearing date set by court
Tax Court (general, over $25K)	Typically 12–24 months to hearing