If the Canada Revenue Agency (CRA) has reassessed your income tax, first identify exactly what changed, then calendar the correct objection deadline and file a formal, issue-specific notice through an accepted channel. For most Canadian federal income-tax reassessments, the ordinary period is 90 days from the date the notice was sent. An individual (other than a trust) and a graduated rate estate may have until the later of that 90-day period and one year after the filing-due date for the year. These rules are Canadian federal examples, not universal deadlines; another country, province, taxpayer category or notice type can follow a different process.
Start by classifying the notice
Do not begin by arguing with the adjustment over the phone. Begin with the document itself. The issuing authority, date sent, tax year, type of determination and response instructions control what you must do next.
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Record the identifying details
- The authority that issued it, such as the CRA.
- The date the notice was sent. This is generally the date from which the federal objection period is calculated.
- The tax year and whether the document is an assessment, reassessment, proposed adjustment, collection demand or another determination.
- Every line, credit, deduction, loss, benefit or amount that changed, together with the resulting balance, refund or interest shown.
- The response address, online route, form number and any special instructions printed on the notice.
A proposed adjustment during an audit is not the same procedural event as an issued reassessment. A reply to an information request, a telephone call, a request for reconsideration or additional audit records does not automatically preserve the formal objection right that follows an assessment or reassessment. CRA identifies a formal notice of objection as the route for disputing a reassessment.
Calculate the Canadian federal deadline immediately
Once you know the notice type and taxpayer category, put the possible dates on a calendar. The federal Income Tax Act and CRA guidance use different rules for different taxpayers.
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| Situation | Deadline described by the source | Authority |
|---|---|---|
| Most taxpayers, including taxpayers other than an individual (other than a trust) or a graduated rate estate | Generally 90 days after the notice of assessment or reassessment was sent | CRA dispute guidance; Income Tax Act, section 165 |
| Individual other than a trust, or a graduated rate estate | The later of 90 days after the notice was sent and one year after the filing-due date for the tax year | Income Tax Act, section 165 |
| Application to the Minister for more time after the ordinary objection period | CRA guidance describes an outer period of one year after the ordinary objection period expires, subject to statutory conditions and reasons for the delay | CRA ITAM Chapter 19; Income Tax Act, section 166.1 |
Use the date printed on the notice and the filing-due date that applies to that tax year and taxpayer. If the notice is unclear, verify the current statute and CRA instructions rather than relying on an assumed 90-day calculation. A deadline is not extended merely because you are still discussing the audit or sending documents informally.
Know what a formal objection must contain
Section 165(1) of the Income Tax Act says: “A taxpayer who objects to an assessment under this Part may serve on the Minister a notice of objection, in writing, setting out the reasons for the objection and all relevant facts.” CRA’s current dispute guidance similarly says: “In all cases, you have to explain why you disagree and include all relevant facts and supporting documents.”
Your objection should therefore be organized by disputed issue, not as a general statement that the assessment is unfair. For each adjustment:
- Identify the adjustment. Quote or describe the CRA line item, amount and tax year exactly enough for the Appeals officer to locate it.
- State your position. Say what amount, deduction, credit, loss or income figure you believe should apply.
- Set out the facts. Give dates, transactions, relationships, business purpose, residency or other facts that establish the point.
- Explain the legal or factual error. Connect the facts to the rule you say CRA misapplied or the evidence it overlooked.
- List the supporting records. Identify each attachment and explain what it proves.
- Specify the correction requested. Ask CRA to vacate, vary or otherwise correct the particular adjustment and recalculate the assessment.
Keep separate issues separate. If one adjustment concerns a medical expense and another concerns employment income, give each its own heading and evidence list. This makes it harder for a valid point to be missed and shows exactly what relief you seek.
Build a complete evidence file
Assemble records before drafting, while the transactions and chronology are still clear. Make a copy of every item you submit and preserve the originals unless the authority specifically requests an original.
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- The original return and schedules for the tax year.
- The assessment or reassessment notice and every prior CRA letter or audit request.
- Information slips, receipts, invoices, bank or investment statements and payroll records relevant to each adjustment.
- Contracts, leases, travel logs, mileage records, employment agreements or other documents that establish the underlying transaction.
- Calculations showing how you reached the corrected amount, with source figures and assumptions visible.
- A dated chronology of filing, CRA requests, your replies and the reassessment.
- Translations or explanatory statements where a document’s terminology, currency or business structure could be misunderstood.
Send legible copies and label attachments so an Appeals officer can match them to the issue and paragraph in your objection. Do not bury a decisive document in an undifferentiated upload. If a record is unavailable, explain what happened, identify substitute evidence and state when you expect to obtain it; do not imply that an unverified reconstruction is an original record.
Draft the objection in a way CRA can act on
Opening identification
At the top, identify yourself or the entity, account or social-insurance details requested by CRA, the tax year, notice date and notice number. State that the document is a notice of objection to the specified assessment or reassessment under the Income Tax Act.
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Use a repeatable format for every issue:
- CRA adjustment: the line and amount as shown on the notice.
- Objection: the corrected amount or treatment you request.
- Relevant facts: a concise chronology tied to evidence.
- Reason: why the adjustment is factually or legally wrong.
- Documents: attachment names or numbers and what each establishes.
Signature and delivery record
Sign and date the objection in the manner required for your taxpayer type. If a representative signs or files it, confirm that the representative’s authority is in place. Keep the final signed version, every attachment, the transmission confirmation and proof of the submission date together in one file.
File through a recognized CRA channel
CRA’s dispute guidance describes two principal routes for the federal process: its online formal-dispute service, or a mailed Form T400A or written objection to the Chief of Appeals at the relevant Appeals Intake Centre. Follow the route and address shown in the current notice and online instructions; addresses and portal procedures can change.
- Prepare the signed objection and a numbered attachment index.
- Use CRA’s online dispute service if it is available for your account and notice, and save the on-screen confirmation or reference number.
- If mailing, use Form T400A or a written notice of objection addressed to the Chief of Appeals at the applicable Appeals Intake Centre.
- Retain a complete PDF or paper copy of what you sent, including file names, page order and the date and time of transmission.
- Preserve independent evidence of delivery, such as the portal confirmation or postal tracking, with the objection file.
Filing an objection does not require you to abandon communication with the audit office, but informal communication is not a substitute for filing. If you discover an additional issue after submission, ask CRA how to add it and check whether the issue is one that can legally be raised in an objection; do not assume every account entry is objectionable.
What happens after filing
CRA Appeals reviews the objection and may request clarification or additional records. Respond by the stated date, keep copies of each response and update your chronology. Record the date CRA sends its objection decision because a later court deadline runs from that date.
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Check the revised assessment or account to confirm that the specific adjustments, interest and resulting balance or refund match the decision. Keep the decision and revised notice with your tax-year records.
If CRA confirms or partly allows the reassessment
CRA’s Guide P148 describes a Tax Court of Canada appeal for an eligible matter. The guide says the Court must receive the appeal within 90 days after CRA sends its objection decision. Check the guide and the decision for the applicable route, permitted issues and filing instructions; not every item appearing on a tax account can necessarily be appealed in the same way.
| Question | Formal objection | Later Tax Court appeal |
|---|---|---|
| Decision-maker | CRA Appeals | Tax Court of Canada |
| Triggering deadline in the covered federal guidance | Generally 90 days after the assessment or reassessment was sent, with the special individual or graduated-rate-estate rule | 90 days after CRA sends its objection decision, according to Guide P148 |
| Record to organize | Notice, reasons, relevant facts and supporting documents | Objection, CRA decision, assessment and the evidence and issues permitted for the appeal |
| Practical considerations | Written reasons and facts are required; file through CRA’s accepted channel | Court procedure, jurisdiction and representation requirements apply; obtain current instructions |
Because a court appeal has its own jurisdictional and procedural rules, read the current CRA guide and court materials promptly and consider qualified Canadian tax advice where the amount or legal complexity warrants it.
If the objection deadline has passed
Act immediately rather than assuming the right is lost or filing an unexplained late letter. Section 166.1 permits an application to the Minister for an extension of time. The application must explain why the objection was late, and CRA guidance describes conditions that include making the application within one year after the ordinary objection period expires.
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Prepare the late-filing request with:
- The assessment or reassessment date and the ordinary deadline.
- The date you learned of the notice or the event that prevented timely filing.
- A chronological, credible explanation for the delay.
- A proposed notice of objection containing the full reasons, relevant facts and supporting documents, not merely a promise to provide them later.
- Evidence supporting the explanation, such as illness, absence, delivery problems or other circumstances, where applicable.
Meeting the outer period does not guarantee an extension. The statutory conditions and the facts of the delay control. If the one-year window is close to expiring, file and obtain advice without waiting for an informal CRA response.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common mistakes that do not preserve an objection
Sending only audit documents
Audit records may help CRA reconsider a proposed adjustment, but they do not necessarily constitute a formal objection after a reassessment. File the required written objection separately and on time.
Writing “I disagree” without particulars
A conclusion without the disputed line, relevant facts, reasons and documents does not give CRA the information the statute and guidance call for. Use an issue-by-issue structure.
Using the wrong date
Taxpayers sometimes count from the day they opened the envelope, called CRA or uploaded a document. The federal rule generally refers to when the notice was sent. Preserve the envelope or electronic notice and calculate from the correct event.
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Requests for reconsideration, calls and promises to send more records do not automatically extend a statutory objection period. Calendar the deadline even while discussions continue.
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Submitting an incomplete record
Missing calculations, illegible receipts and unlabeled attachments slow review and can leave a factual point unsupported. Submit a coherent copy set and retain proof of exactly what CRA received.
Treating every account entry as objectionable
CRA’s Guide P148 identifies limits and invalid objection situations. Confirm that the item and type of determination are legally open to objection before investing in a court strategy.
When professional assistance is sensible
Consider prompt advice from a qualified Canadian tax lawyer, accountant or other authorized tax professional when the amount is substantial, the reassessment alleges fraud or negligence, several years or entities are involved, the legal issue is novel, the deadline is near or the objection is already late. Ask the adviser to confirm the notice type, deadline, filing route, issues preserved and evidence still needed. Professional help is a risk-management choice, not a prerequisite to filing, and no particular provider is endorsed here.
Do not import another country’s deadline
Canadian federal periods do not automatically apply elsewhere. For example, an IRS Tax Tip dated June 23, 2026 describes a 60-day period for disagreeing with certain U.S. math or clerical error notices and asks for supporting records. That is a notice-specific U.S. procedure, not a general American or Canadian reassessment deadline. If your notice comes from another country or a provincial authority, use that authority’s notice-specific statute and filing instructions.
Quick Recap
A practical preservation checklist
- Identify the authority, notice type, tax year, notice date, changed amounts and response channel.
- Calculate every potentially applicable deadline and put the earliest operational date on your calendar.
- Separate informal audit correspondence from the formal objection required for an issued reassessment.
- List each disputed adjustment and the correction you seek.
- Gather the return, notice, correspondence, slips, receipts, statements, contracts and calculations.
- Write the reasons and relevant facts for each issue and connect every assertion to evidence.
- File through the current CRA online service or by Form T400A or written objection to the relevant Appeals Intake Centre.
- Save the exact submission, attachments, confirmation and proof of delivery.
- Track CRA’s decision and, if necessary, the 90-day Tax Court period described in Guide P148.
- If late, prepare the extension application and complete objection immediately, subject to section 166.1’s conditions.
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