A filed return should not be changed by sending a second original return. Once CRA has assessed the filing, a correction is requested through the appropriate adjustment route with the revised amounts and supporting explanation.
Wait for the assessment
CRA instructs taxpayers to wait until the Notice of Assessment is received before requesting a change. A premature duplicate filing can complicate the account.
Record the assessment date and identify the exact return version that CRA processed.
For GTA clients, virtual work can still be thorough when records are indexed, questions are documented and sensitive information moves through an appropriate secure channel. This section is reviewed in the context of taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Define the requested change
An adjustment should state the line, original amount, revised amount and reason. It may also affect connected schedules or credits.
Prepare a before-and-after schedule rather than describing the issue vaguely.
The taxpayer reviews the relevant summary and remains responsible for the truth and completeness of information supplied. Representation authority, where provided, does not transfer that responsibility. The objective is to prepare a precise, supported change request and monitor the resulting reassessment.
Choose the available channel
CRA provides Change my return, ReFILE and paper T1-ADJ options, with restrictions based on year and return type.
Confirm eligibility for the taxpayer and year before selecting the channel.
Material positions should be explainable to someone who did not prepare the file. That means schedules use clear labels, totals reconcile and unusual treatments have a factual basis. This section is reviewed in the context of taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Understand exclusions
Some matters—such as certain elections, personal-information updates, older years or specialized returns—may not be handled through the ordinary online route.
Read the current CRA restrictions and use paper or another process where required.
A deadline plan should distinguish filing, payment, information returns, responses and objection rights because each can follow a different rule. The objective is to prepare a precise, supported change request and monitor the resulting reassessment.
Support the entire amount
CRA may ask for documents supporting the revised claim and, for a paper request, documentation for the entire amount described.
Create a labelled document index tied to the calculation.
For GTA clients, virtual work can still be thorough when records are indexed, questions are documented and sensitive information moves through an appropriate secure channel. This section is reviewed in the context of taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Consider connected years
A changed loss, pension split, tuition amount or carryforward may affect another return.
Map consequential adjustments before submitting isolated requests.
The taxpayer reviews the relevant summary and remains responsible for the truth and completeness of information supplied. Representation authority, where provided, does not transfer that responsibility. The objective is to prepare a precise, supported change request and monitor the resulting reassessment.
Processing expectations
CRA currently publishes different target times for online and paper changes and notes that complex or multiple-year requests can take substantially longer.
Use current processing information and avoid duplicate follow-ups while the request is active.
Material positions should be explainable to someone who did not prepare the file. That means schedules use clear labels, totals reconcile and unusual treatments have a factual basis. This section is reviewed in the context of taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Possible outcomes
CRA may allow all changes, allow part or make no adjustment. The result may be a Notice of Reassessment or explanatory letter.
Compare every accepted line with the request and calculate any remaining disagreement.
A deadline plan should distinguish filing, payment, information returns, responses and objection rights because each can follow a different rule. The objective is to prepare a precise, supported change request and monitor the resulting reassessment.
Refund limits
CRA states that a refund generally cannot be issued for an adjustment requested more than ten calendar years after the relevant tax year. Other limits may also matter.
Flag older years before investing in a claim and obtain specific advice.
For GTA clients, virtual work can still be thorough when records are indexed, questions are documented and sensitive information moves through an appropriate secure channel. This section is reviewed in the context of taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
After reassessment
Update carryforwards, balances and later returns with the final result. If CRA disagrees, correction, additional evidence or objection may be considered within applicable limits.
Do not let an unresolved adjustment disappear from the next year’s opening data.
The taxpayer reviews the relevant summary and remains responsible for the truth and completeness of information supplied. Representation authority, where provided, does not transfer that responsibility. The objective is to prepare a precise, supported change request and monitor the resulting reassessment.
Why this issue deserves a separate review
The practical difficulty is rarely the form title alone. It is the connection between facts, evidence, tax classification and CRA account history. A careful process makes those connections visible before a filing position is finalized. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
For GTA clients, virtual work can still be thorough when records are indexed, questions are documented and sensitive information moves through an appropriate secure channel. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
How the engagement is organized — 2
The file is scoped by person, year, deadline and deliverable. Available records are inventoried, missing information is identified and assumptions are separated from verified facts. This prevents work from advancing on an unstable foundation. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
The taxpayer reviews the relevant summary and remains responsible for the truth and completeness of information supplied. Representation authority, where provided, does not transfer that responsibility. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
Evidence and professional judgement — 3
Tax preparation requires judgement about relevance and classification, but judgement is not permission to invent evidence. Where a document is unavailable, alternative support and the limits of any reconstruction should be recorded. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Material positions should be explainable to someone who did not prepare the file. That means schedules use clear labels, totals reconcile and unusual treatments have a factual basis. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
Deadlines and changing guidance — 4
Tax dates, online-service availability and administrative policy can change. Time-sensitive statements on this page must be confirmed against the current CRA publication for the applicable year. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
A deadline plan should distinguish filing, payment, information returns, responses and objection rights because each can follow a different rule. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
Why this issue deserves a separate review — 5
The practical difficulty is rarely the form title alone. It is the connection between facts, evidence, tax classification and CRA account history. A careful process makes those connections visible before a filing position is finalized. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
For GTA clients, virtual work can still be thorough when records are indexed, questions are documented and sensitive information moves through an appropriate secure channel. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
How the engagement is organized — 6
The file is scoped by person, year, deadline and deliverable. Available records are inventoried, missing information is identified and assumptions are separated from verified facts. This prevents work from advancing on an unstable foundation. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
The taxpayer reviews the relevant summary and remains responsible for the truth and completeness of information supplied. Representation authority, where provided, does not transfer that responsibility. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
Evidence and professional judgement — 7
Tax preparation requires judgement about relevance and classification, but judgement is not permission to invent evidence. Where a document is unavailable, alternative support and the limits of any reconstruction should be recorded. In a t1 adjustments engagement, the analysis is directed toward prepare a precise, supported change request and monitor the resulting reassessment. The relevant population includes taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment.
Material positions should be explainable to someone who did not prepare the file. That means schedules use clear labels, totals reconcile and unusual treatments have a factual basis. The working file records the question, evidence received, calculation performed, conclusion reached and any follow-up assigned to the taxpayer.
Official information and review date
Content reviewed July 22, 2026. Confirm changing dates and procedures with the Canada Revenue Agency: personal tax due dates, changing a return, and the relevant CRA program page for the issue.
Frequently asked questions
Who is this service for?
It is designed for taxpayers who found a missing slip, incorrect amount, omitted deduction or other error after receiving an assessment. The engagement is confirmed only after the years, issues and available records are reviewed.
Can this be completed virtually?
Yes. Toronto and GTA clients can meet by telephone or secure virtual appointment. Sensitive records should not be sent through the public contact form.
What records are normally required?
The exact list depends on the issue. It commonly includes the filed return or draft, CRA notices, tax slips, supporting schedules, receipts, account statements and a chronology of relevant changes.
Can GTA Accountant guarantee CRA acceptance?
No. Filing and administrative outcomes depend on the facts, law, evidence and CRA processing. The service is designed to create an accurate and supportable submission.
Does submitting a form create an engagement?
No. Scope, responsibilities, timing and fees must be accepted separately before professional work begins.
When should I get help?
Seek assistance early when a deadline, several years, foreign property, a major transaction, missing evidence or CRA correspondence is involved.
Professional limitation
This page provides general Canadian tax information. It is not legal advice or an opinion on a particular taxpayer. Voluntary disclosure, objection, litigation, privilege or prosecution-risk questions may require a Canadian tax lawyer.