CRA Desk Audit vs. Field Audit: What's the Difference in Ontario?

Not every CRA audit looks the same. Some are handled entirely by mail, with the CRA's auditor never leaving their own office. Others involve an auditor coming to your business, sitting down with your books, and asking questions in person. Both are genuinely audits — a step up from a routine review letter — but the process, the documents involved, and the level of preparation each one calls for are quite different.

This guide explains the difference between a desk audit and a field audit, what tends to trigger either one, and what Ontario taxpayers should expect and do in each case.

Two Ways CRA Conducts an Audit

A desk audit is conducted primarily by correspondence — mail, fax, an online portal, or phone — from the CRA's own office. The auditor requests specific documents and information, you provide them, and the exchange continues until the matter is resolved or CRA proposes an adjustment. You typically never meet the auditor in person.

A field audit involves the auditor visiting a physical location — your business premises, your home office, or your accountant's office — to review books and records directly, often over more than one visit. Field audits tend to be broader in scope and are more common for business owners, self-employed individuals, and returns involving more complex records than a straightforward employment-income return.

This is a different distinction from the one between a CRA "review" and an "audit" — a review (such as a matching-program letter asking for a receipt) is a lighter-touch check that comes before either kind of audit. Desk and field audits are both formal audits; they differ in how the audit is carried out, not in whether it's an audit at all.

What Triggers Either Kind of Audit

CRA selects returns for audit through a range of methods, including industry-based risk-scoring, unusual deduction or expense patterns compared to similar taxpayers, issues flagged through foreign-property reporting, information received from third parties, and random selection. Being selected for either a desk or field audit is not, on its own, an accusation of wrongdoing — it can simply reflect how your industry, return pattern, or file happened to be flagged.

What to Expect: Desk Audit

1. A letter or online request identifying the specific years, issues, or items under review, and the documents needed to support them.
2. You gather and submit copies of the requested documents — receipts, invoices, contracts, or bank records — by mail or through CRA's online systems.
3. The auditor reviews what's submitted and may come back with follow-up questions or requests for additional documentation.
4. If the auditor intends to make an adjustment, you generally receive a proposal letter explaining the intended changes and an opportunity to respond before anything is finalized.

What to Expect: Field Audit

1. Initial contact establishing the scope of the audit — which years, which type of return, and generally which issues are of concern.
2. On-site review of your books and records, which may take place over multiple visits depending on the complexity of your affairs.
3. The auditor may interview you or staff members, and review supporting materials such as contracts, leases, and bank statements in more depth than a desk audit typically involves.
4. As with a desk audit, unresolved issues generally lead to a proposal letter and a chance to respond before a formal reassessment.

Your Rights and Practical Preparation

• [ ] Confirm the auditor's identity and ask them to clearly state the scope of the audit — which years and which issues
• [ ] Organize your records before handing anything over; provide what's requested, not your entire filing history
• [ ] You're entitled to have a lawyer or accountant represent you, or be present during meetings and site visits
• [ ] Ask for reasonable time to gather and respond to document requests rather than agreeing to an unrealistic deadline
• [ ] Keep your own complete copy of everything you provide to the auditor

After the Audit: If You Disagree

Whether an audit is conducted by desk or in the field, a disputed result follows the same path: if CRA reassesses your return, you can file a Notice of Objection with the CRA's Appeals Branch — an administrative step, not a court filing — and, if the objection doesn't resolve the matter, appeal to the Tax Court of Canada afterward.

It's also worth knowing that CRA generally can't reassess indefinitely. As of mid-2026, the normal reassessment period is three years for individuals and Canadian-controlled private corporations, and four years for other corporations and mutual fund trusts, running from when the original assessment was sent — though CRA can reassess outside that window in specific circumstances, such as misrepresentation or a signed waiver. Confirm the current rules with a tax professional if timing is at issue in your case.

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