Understanding Tax Audits in Canada

By L.Kenway BComm CPB Retired
This is the year you get all your ducks in a row! Start by starting ... and keep it simple. Consistency beats perfection.

Updated April 15, 2026  |  Originally published on Bookkeeping-Essentials.com in 2011.

WHAT'S IN THIS ARTICLE
1. Introduction | What's New In 2026 | 2. Tax Review Process | 3. Tax Audit Process | 4. When You Want To Amend A Tax Return | 5. Highlights Of This Post | 6. Related Reading

NEXT IN SERIES >> CRA Audit Trails: Why you want them
BACK TO >> Self-Employed Audit-Ready Books

At A Glance

This page explains how CRA's review and audit process works ... what the notices mean, what triggers audit scrutiny, and what to so when CRA contacts you. Use the jump links to go straight to what you need.

What's New In 2026
CRA's processes can change in any given tax year. Key updates are noted in this box and integrated into the article's content.

Jump To >> What's New In 2026

What It Means To Sign Your Return
Who is responsible for the data in the tax return you send to the CRA, you or your tax preparer? You may be surprised

Jump To >> Signing Your Income Tax Return

What Triggers An Audit
Sometimes random. More often, something in your return draws attention. You'll find the full breakdown on it's own page.

Jump To >> What Triggers An Audit

Tax Review Process
During reviews, CRA tries to educate you, the taxpayer, in addition to verifying your income reported. If you receive a request for documentation or receipts, it does not mean you are being audited. This section covers the pre-assessment review, your Notice of Assessment (NOA), processing reviews, and the matching program ... and what each one means for you.

Jump To >> Tax Review Process

Tax Review Process
Business returns are often selected randomly based on computer generated lists of audit projects testing a particular group of tax payers identified as having high non-compliance.

Insight Accounting explains that "as of 2026, the Canada Revenue Agency (CRA) uses artificial intelligence (AI) and machine learning as a fully operational, high-powered triage system to screen millions of tax returns in real time for audit selection. These systems systematically score returns based on hundreds of variables to detect anomalies, patterns, and non-compliance, allowing the CRA to shift from random audits to targeted, risk-based interventions".

How returns get selected, the difference between an office / desk audit and a field audit, and what to do if you receive a Notice of Reassessment.

Jump To >> Tax Audit Process

Good Compliance Habit: Amending Your Return
Caught an error after filing? Fix it yourself before  CRA finds it. Hop on over to the full article on the how and why.

Jump To >> Amending Your Return

Canada's tax system depends on self-assessment and self-reporting by taxpayers. The Canada Revenue Agency (CRA) conducts review activities to determine compliance. 

• What it means when you sign your tax return
• What triggers tax audits in Canada

Tax Review Process

During reviews, CRA tries to educate you, the taxpayer, in addition to verifying your income reported. If you receive a request for documentation or receipts, it does not mean you are being audited. 

• The difference between a review and an audit
• The pre-assessment review
• The notice of assessment
• The processing review

Tax Audit Process

Business returns are often selected randomly based on computer generated lists of audit projects testing a particular group of tax payers identified as having high non-compliance.

• How returns are selected for a tax audit
• Office audit vs. field audit
• What happens in tax audits
• The notice of re-assessment

Good Compliance Habit

• Why you want to amend your tax return for omissions or errors

Now let's look at what we will be looking at in detail. I've broken it into two sections:

• The Review Process = CRA is checking specific items on your return and educating you about compliance
• The Audit Process = CRA is doing a deeper examination of your records and reporting

Both require prompt attention. The difference is the depth of scrutiny, not whether the matter is serious.

Jump To >> Pre-Assessment Review | NOA | Processing Review | Matching Program | Recap

CRA Review vs. CRA Audit: Not the Same Thing

Not every letter from the CRA means you are being audited.

In many cases, the CRA starts with a review, not a full audit. A review is usually a request to confirm specific information on your return, such as deductions, credits, receipts, or other supporting documents. It is part of the CRA's normal compliance process.

A review also has an educational component. In many cases, the CRA is not only verifying the information filed, but also helping the taxpayer understand what records are required and how the rules apply. That said, a review should still be taken seriously. If you do not respond properly, or cannot support what you claimed, the result can still be adjustments, interest, penalties, or further scrutiny.

An audit is more serious and more detailed. If you are being audited, you will receive a notice explaining that you have been selected for an audit. Arrangements will then be made for a meeting to begin the audit.

That point matters. In an age of email fraud, phone scams, and cybercrime, you should know that a real audit is not something you are expected to guess at. The CRA will contact you and identify that an audit is beginning.

During an audit, the CRA may examine your books, source documents, bank records, invoices, receipts, and logs to verify that what you filed is accurate.

Why the difference matters
If you receive a review letter, do not ignore it just because it is 'not an audit'. Reviews can still lead to adjustments, interest, penalties, or further scrutiny if you do not respond properly or cannot support what you claimed.

If you receive an audit notice, do not assume you should handle it alone just because the request looks straightforward. Audits can involve nuances in what the CRA is really asking for, how records should be presented, and what follow-up questions your response may trigger.

When to get professional advice
If the CRA notifies you that you are being audited, consider speaking with an accountant or qualified tax professional before responding.

An audit request may look straightforward, but there may be issues or risks you do not recognize. Professional advice can help you decide how to approach the audit, what documents should be submitted, and how to avoid creating new problems through an incomplete or poorly framed response.

What to do now
If you receive any CRA letter:

1. confirm whether it is a review request or an audit notice
2. record the deadline immediately
3. keep the CRA reference number and include it in your response
4. gather the documents that support the amounts filed
5. keep copies of everything you send
6. if it is an audit, consider getting professional advice before responding
   

The Pre-Assessment Review

After you file your return, the CRA usually does a pre-assessment review before issuing your Notice of Assessment. It is not the same as a full audit.

If you file electronically, you may receive an Express Notice of Assessment (Express NOA) almost immediately through your tax software or CRA portal. That speed can be reassuring, but it does not mean CRA has finished validating everything on your return. Express NOA is a fast initial assessment, not a guarantee that the return will never be reviewed again.

This is an early review step. At this stage, the CRA is generally checking for obvious issues such as:

• arithmetic errors
• missing information
• certain deductions or credits that may need a closer look

The pre-assessment review is part of CRA's normal processing of returns. If no major problems are found, the CRA will issue your Notice of Assessment and, if applicable, release your refund

Why this matters
Some taxpayers assume that once a refund arrives, everything is final. Not necessarily.

A pre-assessment review is an early check, not the end of CRA scrutiny. More detailed reviews can still happen later. So if you receive a refund, treat it carefully until you are confident there are no missing slips, unsupported claims, or other issues that could lead to an adjustment.

Practical reminder
If you know your return was rushed, based on incomplete records, or filed before all slips were received, do not assume an early Notice of Assessment means the matter is over. The peak period for doing this type of assessment is February to July during tax season, but they can occur year-round.

The Notice of Assessment

After you file your tax return, one of the first official documents you will receive from the CRA is your Notice of Assessment (NOA). It normally arrives about two (for electronic returns) to eight weeks (for paper-filed) after you file your return. If you eFile, you should get an Express NOA almost immediately in your My Account mail portal.

This is the CRA's formal summary of how your return was processed. It shows whether your return was accepted as filed or whether the CRA made adjustments to your numbers.

If no problems were found during the initial processing of your return, the Notice of Assessment will generally confirm the amounts you reported. If the CRA changed something, the notice will explain the adjustment. That may mean:

• additional tax owing
• reduced refunds
• interest charges
• penalties, in some cases

Why this notice matters
Many taxpayers assume the Notice of Assessment means everything is settled. Not necessarily.

A Notice of Assessment tells you how the CRA processed your return at that stage. It does NOT guarantee the return will never be reviewed again. Processing reviews, matching reviews, and audits can still happen later.

That is why you should not treat the notice as permission to stop paying attention to your records.

Digital delivery matters now
As of 2026, CRA defaults notices to My Account or My Business Account with an email notice telling you to check your portal.

That means a notice is considered to be delivered when it appears in your CRA mail portal, even if you have not opened it yet. Your objection deadline response time starts running immediately.

If you disagree with the Notice of Assessment
If you believe the CRA made an error, DO NOT IGNORE IT.

Review the notice carefully and compare it to the return filed. If a professional prepared your return, contact them right away. CRA assessors can make mistakes, and objection deadlines should never be allowed to expire while everyone assumes the notice is correct.

If necessary, you may need to file a Notice of Objection within the allowed time limit. As a general rule, you have until the later of:

• 90 days after the date on the Notice of Assessment, or
• one year after your filing due date*

*If you are self-employed, that filing due date is generally June 15.

The Processing Review

A processing review happens after your return has already been assessed. This is still part of the review process. It does not automatically mean you are being audited.

This is a more detailed follow-up review than the pre-assessment check. At this stage, CRA may look more closely at specific deductions, credits, or claims and ask you to provide supporting documents.

That means even if you already received your Notice of Assessment (or even an Express NOA) CRA may still come back and ask questions later. 

What CRA may ask for
In a processing review, CRA may request support such as:

• receipts
• invoices
• mileage logs
• schedules or worksheets
• proof for deductions or credits claimed

A key change in 2026
Before April 2026, many processing reviews happened mainly after tax season. That is no longer a safe assumption.

As of April 2026, CRA is conducting processing reviews on a year-round basis. In other words, requests for supporting documentation can now show up at any time of year.

Why this matters
A processing review can feel unsettling because it arrives after you thought the return was already dealt with. But this is exactly why you should not assume a Notice of Assessment means everything is final.

If CRA asks for supporting documents and you cannot provide it, the review may lead to:

• denied deductions or credits
• adjustments to your return
• added tax
• interest
• possible penalties in some situations

Digital delivery matters here too
If you authorized a tax preparer to receive CRA correspondence, they may be able to view the letter through Represent a Client.

Otherwise, remember that CRA delivery of notices defaults to your My Account or My Business Account mail portal. The notice is considered delivered once it appears in your portal, whether or not you have opened it.

What to do now
If you receive a processing review letter:

1. read it carefully
2. note the deadline immediately
3. locate the CRA reference number
4. gather the exact documents requested
5. keep copies of everything you send
6. respond completely and on time

Practical tip
Every CRA review letter includes a reference number, usually near the top right of the letter.

Always include that reference number in your written response and in any documents you submit. It is how CRA tracks your specific file and inquiry.

If someone phones you claiming to be from CRA, they should be able to give you that reference number. If they cannot, treat the call cautiously.

You can submit requested documentation electronically through My Account if you are registered, or through Represent a Client if you use a tax professional as your authorized representative.

The Matching Program

CRA's matching program compares the information on your tax return to information it receives from third parties such as employers, financial institutions, or platform economies. That includes things like:

• T-slips
• employer reporting
• financial institution reporting
• other mandatory information-sharing sources

In simple terms, CRA checks whether the income and credits reported on your return match the information it has already received from other sources.

The matching program typically runs after returns have already been filed and assessed. It typically runs between September and March. That is why a taxpayer may receive a Notice of Assessment, think everything is settled, and then later hear from CRA when the numbers do not line up.

An Example
A problem happens often is when a taxpayer files their return ... and then later receives an additional T-slip, usually a T3 or T5 for a self-employed worker, but never adjusts their filed return.

When CRA's matching program compares the filed return to the slip information it received, the omission may be caught and the return may be adjusted.

For small business owners, an issue arises when platform, gig, or sharing economy income is not fully reported.

Why this matters
Its goal is to ensure the correct net income for tax purposes is reported ... as many of Canada's federal and provincial tax credits and benefits are dependent on this number. If CRA finds income that was not reported, it may:

• adjust the return
• issue a Notice of Reassessment
• charge additional tax
• add interest
• apply penalties in repeated cases

This is why it is usually better to correct an error yourself than wait for CRA to find it first.

The matching program can also work in your favour. If CRA finds that you under claimed certain amounts, such as some CPP-related credits or tax deducted at source, it may adjust the return and issue an additional refund where appropriate.

So the matching program is not about punishment. Its purpose is to make sure the return reflects the information CRA has on file.

Jump To >> How Returns Are Selected | What Happens During An Audit | The Notice of Reassessment | If It Becomes a Dispute | Recap 

How Returns are Selected For A Tax Audit in Canada

Many taxpayers assume audits happen out of the blue. Sometimes a return is selected randomly. But more often, a return is selected because something in it draws attention, does not match other information available to the CRA, or fits a pattern the CRA is already watching more closely.

In 2026, CRA's artificial intelligence (AI) audit systems are fully operational. they are no longer in pilot project. Automated screening algorithms now review millions of returns in real time, flagging discrepancies and selecting files for audit at a scale and pace that human reviewers alone could never achieve.

Why CRA selects some returns for closer scrutiny
In addition to AI, the CRA uses a mix of review programs, matching systems, audit projects, and data analysis to identify returns that may need more attention.

Individual and business returns may be selected for closer review or audit for reasons such as:

• information that does not match third-party reporting
• deductions or credits that appear unusual for the industry or filing situation or are actively monitoring
• a prior audit or review that resulted in adjustments
• random selection based from CRA audit projects targeting a particular group of tax payers identified as having high non-compliance
• association with other taxpayers or businesses already under review
• leads arising from other audits, investigations, or informants
• AI-driven risk scoring and data analytics that flag statistical outliers and predictive modelling to prioritize files by risk levels.
• Lifestyle analysis ... AI can now aggregate data from multiple sources to compare reported income against lifestyle far more effectively than manual review could.

The good news is CRA's AI systems are designed to identify patterns of non-compliance, error, and evasion ... not to catch honest taxpayers making reasonable claims. If your books are clean, and your documentation solid, AI driven selection means audit resources are directed at non-compliant filers rather than distributed randomly. That said, clean books in the age of AI driven audits demands a higher standard than it used to..

CRA has stated that its AI systems operate under human oversight. This means no audit action is taken based solely on algorithmic output. But that's cold comfort if your records can't support what you filed.

What this means in practical terms
Being selected does not automatically mean wrongdoing. It does mean something about the return, the reporting pattern, or the surrounding information caused the CRA to take a closer look.

That is why good recordkeeping matters so much. If your return is selected, you need to be able to show that the income reported, deductions claimed, and filings submitted are supported by proper records. If your records are weak, that is where a manageable issue can become a more serious one.

If your return is selected, it is the return itself ... and the supporting records behind it ... that matter.

No distinction is made based on how the return was filed or who prepared it.

What to do now
To reduce risk and improve your position if CRA asks questions later:

1. report ALL income completely
2. avoid estimates or rounded claims unless properly supported
3. keep receipts, logs, and source documents
4. make sure deposits, invoices, and reported income can be traced
5. review unusual deductions carefully before filing

Practical tip
Good records are your best protection in any CRA review or audit. If you are not sure what that looks like in practice, read How to Create CRA Audit Trails.

Why does every deposit need an explanation? Because unsupported deposits may be treated as income unless you can prove otherwise. Read Simple Audit-Proofing for Family Deposits and Transfers for this important tip.

If you want to understand the most common issues that draw CRA attention, read >> What Triggers Tax Audits in Canada.

Office Audit vs. Field Audit: Not The Same Thing

If your return is selected for a tax audit, the auditor will conduct either an office audit or a field audit.

• An office audit (also called a desk audit) is handled from CRA’s office. You provide the requested documents ... today, usually by secure online submission, correspondence, phone, or email rather than an in-person visit. CRA doesn’t generally consider this a true audit; it sits closer to the review end of the spectrum.
• A field audit is more thorough. The auditor comes to your place of business ... or meets with your accountant or authorized representative ... at a pre-arranged time to examine your records in detail.
  
  A pre-arranged time and place matters. In an age of cybercrime, scams, and fake CRA contacts, you should know that a real audit does not begin with guesswork or panic. The CRA will contact you and identify that an audit is starting.
  

Either way, you will be notified in advance. This is not a surprise doorstep visit.

If you have an accountant or authorized representative, they can meet with the auditor on your behalf. You don’t have to handle it alone.

Next step: Brush up on CRA’s business record retention requirements.

What Happens During A Tax Audit In Canada?

Part 2. What CRA looks at

The auditor’s purpose is to verify that the income reported, deductions claimed, and tax filings submitted are accurate and backed by records.

during an audit, the CRA may examine records such as:

• ledgers and journals
• bank statements and deposit records
• sales invoices and expense receipts
• contracts and agreements
• GST/HST records
• payroll records
• mileage logs and other supporting schedules

Any unsupported claims will usually be denied. If your records are weak, incomplete, inconsistent, or unsupported, adjustments ... plus interest, and penalties ... follow. That means you will likely also owe more tax.

An audit is not cause for alarm in itself. It is a compliance process. If your records are organized and your filing is supportable, the audit may simply confirm that your reporting is in order. Where audits become serious is when there are weak records, unsupported claims, underreported income, or tax avoidance or tax evasion.

It also helps to remember that the auditor is a human being. First impressions matter. One of the best first impressions you can make is to provide well-organized records, clearly labeled documents, and the information requested. That tells the auditor you take the process seriously and are prepared to support what you filed. It starts the audit on a good path.

The auditor will make proposals during the audit. Always ask for those proposals in writing. You’ll have 30 days to respond, and your response will be considered before any reassessment is issued.

--- Historical Note

Income tax audits used to be combined with GST audits. That practice ended in 2010 when BC and Ontario introduced HST. If you have both income and GST/HST issues, expect separate processes.

--- End Note

Do not treat an audit casually
An audit is not the time to guess, fill gaps from memory, or send documents without thinking through what they show.

Even when the CRA request appears straightforward, there may be nuances in:

• what the CRA is really testing
• how documents should be organized and presented
• what new questions your response may trigger
• whether a document helps your position or weakens it

When to get professional advice
If you are being audited as opposed to being reviewed, it would be prudent to contact an accountant or qualified tax professional before you respond.

An audit may look straightforward on the surface, but there may be issues or risks you do not recognize. A professional can help you assess:

• the scope of the audit,
• decide how to approach it, 
• determine what documents should be submitted, and 
• communicate with the CRA more effectively.

What happens as the audit moves forward
As the audit progresses, the auditor may raise issues or propose adjustments based on the records reviewed.

If that happens, your accountant will:

• ask for proposals or concerns to be put in writing
• review them carefully and discuss them with you
• respond within the deadline given
• provide support for your position where possible

You are generally given an opportunity to respond before a reassessment is finalized.

Next step if you receive an audit notice
If you receive a notice saying you are being audited, follow a clear process rather than reacting emotionally.

Related reading >> What To Do If You Receive a Notice Saying You Are Being Audited

The Notice of Reassessment

If the audit results in changes to your return, CRA will issue a Notice of Reassessment (NOR). Like the original NOA, this is an official document ... keep it with your records.

If you disagree with the reassessment, the same objection process applies. You have until the later of 90 days from the reassessment date or one year from your original filing due date to file a Notice of Objection. Don’t let that deadline slide.

For more detail on what to do after an audit notice arrives ... including your rights as a taxpayer:

Jump To >> Responding to a Tax Audit Notice

Jump To >> Taxpayer Bill of Rights

A NOR can also issued when the CRA changes a return that has already been assessed. This can happen after:

• a review
• a matching program adjustment
• an audit
• an amendment request
• new information coming to the CRA's attention

Remember, a reassessment means the CRA has revisited the return and changed one or more amounts. That change may result in:

• more tax owing
• added interest
• penalties
• or, in some cases, a refund if the correction is in your favour

Part 2. Why deadlines matter

Why a reassessment should never be ignored
A reassessment is NOT routine paperwork. It is a signal that the CRA has changed your file. If you receive one, you need to understand:

• what changed
• why it changed
• whether the change is correct
• what deadline applies if you want to challenge it

If you agree with the change, deal with any balance owing promptly to reduce additional interest. If you disagree, act quickly. Deadlines matter.

How long CRA can usually change a return
As a general rule, the CRA can usually reassess a return for up to three years after the original Notice of Assessment is issued.

You may hear this referred to formally as the statute of limitations. In practical terms, it is the usual time limit for how long CRA has to go back and change a return.

That time limit can be longer in some situations. For example:

• if there is suspected misrepresentation or fraud, there may be no time limit
• if the return involves items such as carrybacks or investment tax credits, the period may extend to six years

Why these time limits matter
Many taxpayers make one of two mistakes:

• they assume a Notice of Assessment means everything is final
• they miss the objection deadline because they do not realize the clock is already running

Both mistakes can be costly.

If you disagree with a reassessment
If you believe CRA made an error, do NOT set the notice aside and hope to deal with it later. Read it carefully. Compare it to the original return, the supporting documents, and any earlier CRA correspondence.

If a tax professional prepared the return or helped you respond to CRA, contact them right away. CRA assessors can make mistakes, and objection deadlines should never be allowed to expire while everyone assumes the notice must be correct.

A quick note on objections and appeals
If you disagree with the reassessment, you may need to file a Notice of Objection within the allowed time.

Once you receive your reassessment notice, arrange to pay any additional tax, interest and penalty charges. If you disagree with the notice ... you have 90 days from the date of the notice to file a Notice of Objection.

If the matter continues beyond that stage, there is also an appeal process through the courts.

Tax audits in Canada have an appeal procedure. You can find great pictorial overviews of both the informal procedure and general procedure for notices of appeal on the Tax Court of Canada website. See what happens after filing the first document. Please click because it is worth reading.

What to do now
If you receive either notice:

1. read it carefully
2. identify whether CRA accepted or changed your return
3. note any deadline immediately
4. keep the notice with your tax records
5. compare the notice to the return filed
6. if something looks wrong, get advice before the deadline expires

Related reading >> Relevant Moving Timelines

Understanding Tax Audits in Canada

Reduce your fear of tax audits by understanding the process. It is your responsibility to have knowledge of and apply the tax laws correctly, whether your return was prepared by a professional or not.

In Canada, we have a self assessing and self-reporting tax system. If you are caught evading tax, it is a criminal offense. Under tax law (unlike criminal law), you are guilty until proven innocent.

Small business owners have a higher likelihood of getting audited than an employee because they have to remit their own source withholdings. Possible types of tax audits a small business owner may be subjected to are Office, Field, GST HST, or Payroll.

Audit proof books are your best defense.

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