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
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intro

Tax audits and CRA reviews can have serious financial consequences if you ignore notices, keep weak records, or assume a mistake will go unnoticed. This page explains how the CRA review and audit process works, what the different notices mean, and why getting organized early matters.

Canada's tax system is built on self-assessment and self-reporting. That means you are responsible for reporting your income correctly, claiming only what you can support, and keeping records that back up your return. Because the system relies on public compliance, the Canada Revenue Agency (CRA) carries out reviews and audits to check that tax law is being followed. It is not a personal attack.

One hard truth many small business owners do not realize until it is too late is this ... in tax matters, ignorance of the rules is generally not a defence. If the CRA reviews your return or starts an audit, you may be asked to support what you filed with documents, receipts, logs, and records. If you cannot support your claim, adjustments, interest, and penalties can follow.

That does not mean every CRA letter is an audit. Some contacts are part of the normal review process. But every notice should be taken seriously and dealt with promptly.

If you are self-employed, the risk is often higher than it is for an employee because you are responsible for managing your own tax compliance. Depending on your situation, CRA scrutiny may involve an income tax review, office audit, field audit, GST/HST review, or payroll review.

Your best protection is simple but not optional ... accurate records, organized documents, filing reports on time, not spending monies held in trust, and prompt responses to CRA.

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.

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.

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

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

• information that does not match third-party reporting
• missing information found through CRA's matching programs
• deductions or credits that appear unusual or are monitoring
• a prior audit or review that resulted in adjustments
• claims that do not fit expected patterns for that industry or situation
• random selection based on computer generated lists of audit projects testing 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

For business returns, the CRA may also group returns by industry, filing patterns, or known areas of non-compliance and then select certain files for more detailed review.

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:

• whether you filed electronically or on paper
• whether you prepared the return yourself
• whether a professional prepared it for you

A useful mindset
Do not think in terms of "How do I avoid ever being noticed?" A better question is "If CRA looks at this return, can I support it?" That mindset leads to better habits, better records, and fewer unpleasant surprises.

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.

Good records are not bureaucracy ... they are protection.

What Happens During A Tax Audit In Canada?

Part 1. How an audit starts

If the CRA selects your return for an audit, you will be notified that you have been chosen for audit. Arrangements will then be made for a meeting to begin the audit.

That point 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.

If you have an accountant or authorized representative, the auditor may meet with your accountant instead of you. In either case, the meeting takes place at a pre-arranged time and place, with the necessary supporting documents available for review.

Office audit vs. field audit: Not the same thing
A tax audit is a detailed examination of your records to verify that the income reported, deductions claimed, and tax filings submitted are accurate and supported.

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

• In an office audit (also referred to as a desk audit) the CRA reviews your records from its office, and you provide the requested information. Today, many office audits are handled by correspondence, secure online submission, phone, or email rather than through an in-person visit.
  
  Office audits are generally part of the review process, and CRA does not usually view them as a true audit. They tend to reserve that honour for the field audit.
• In a field audit, the auditor meets with you, or with your accountant or representative, at a pre-arranged time and place to examine your records in more detail.

Part 2. What CRA looks at

The auditor wants to determine whether your records support what you filed. Therefore, during an audit, the CRA may examine records such as:

• ledgers and journals
• bank statements and deposit records
• sales invoices
• 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 incomplete, inconsistent, or unsupported, the CRA may deny deductions, adjust income, and assess additional tax, interest, and penalties.

Just a bit of history ... income tax audits in Canada used to be combined with a GST audit. That practice stopped in 2010 when BC and Ontario introduced HST. I only mention this because some business owners may still assume everything will be reviewed together in one convenient process. That is no longer the case.

Part 3. How to handle it well

An audit is not, by itself, a cause for concern. It is a compliance process. If your records are organized and your filings are supportable, the audit may simply confirm that your reporting is in order.

Where audits become serious is when the taxpayer has weak records, unsupported claims, underreported income, or has engaged in 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.

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

Part 1. What a reassessment is

A Notice of Reassessment is 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

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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