A GST/HST audit feels, at first, like an accounting exercise. The Canada Revenue Agency asks for invoices, returns, and ledgers, and the file appears to be a reconciliation between what was reported and what the books show. That impression is misleading. A meaningful share of GST/HST reassessments turn on legal-characterization questions — was a supply taxable, zero-rated, or exempt; were the place-of-supply rules applied correctly; did the export documentation actually support zero-rating; do the input tax credits have adequate supporting documentation under section 169(4) of the Excise Tax Act and the Input Tax Credit Information (GST/HST) Regulations? The dollars look like accounting, but the analysis is legal.
This guide explains what tends to draw a GST/HST audit, how the audit unfolds, what documentation the CRA expects, the adjustments that recur most often, and how to carry a disputed assessment through the objection process. It is written for registrants and the accountants who support them. It is general information, not legal advice for a particular file.
Why GST/HST audits are different from income tax audits
An income tax audit usually asks whether an expense is deductible, whether a receipt is taxable, whether a transaction occurred at fair market value, and whether penalties apply. A GST/HST audit layers a second set of questions on top: was the supply taxable, zero-rated, or exempt; was the recipient resident or non-resident; did the place-of-supply rules produce the result the registrant assumed; did the export documentation establish that goods actually left Canada; and are the claimed input tax credits supported by the specific documentary requirements the regulations impose?
These are not bookkeeping questions. They are questions about how the Excise Tax Act characterizes a transaction. A registrant can have immaculate books and still face a substantial reassessment because a category was wrong — because a service treated as a zero-rated export was, on the facts, a domestic taxable supply, or because an input tax credit was claimed on a receipt that did not carry the supplier's registration number. Treating the audit as a reconciliation, rather than as a series of legal-characterization questions, is one of the most common and costly errors.
Common GST/HST audit triggers
The CRA does not disclose the full mechanics of its risk-scoring, but the patterns that tend to draw GST/HST scrutiny are well established:
- Cash-intensive industries. Restaurants, taxis and rideshare, trades and contractors, and similar sectors are reviewed more frequently because under-reporting of taxable sales is harder to detect from third-party data alone.
- Large input tax credit claims relative to taxable supplies. A registrant claiming substantial ITCs against modest reported sales — or repeatedly filing in a refund position — attracts attention, because the credit side is where over-claiming concentrates.
- Repeated refund claims. Net-refund filers (exporters, builders before sales, start-ups in a build phase) see more pre-payment and post-payment review than registrants who consistently remit.
- New housing and rental rebate filings with documentary inconsistencies. Rebate claims where the stated intention, occupancy timing, or supporting documents do not line up are a recurring audit and reassessment source.
- Real-estate transactions involving non-residents. A non-resident vendor of taxable Canadian property can carry both a section 116 income-tax obligation and a GST/HST exposure, and the two often surface together.
- Imports and exports without matching documentation. Zero-rating claimed on exports that the carrier and customs records do not corroborate is a frequent target.
- Sector campaigns. The CRA periodically runs industry-wide projects, and a registrant can be selected simply because it operates in the sector currently being examined.
A trigger is not a verdict. Many audits selected on these criteria close with little or no adjustment. The point of understanding the triggers is to keep the documentation that answers the anticipated questions before the audit ever begins.
The audit process, stage by stage
A GST/HST audit follows a recognizable arc, and each stage carries its own deadlines and tactical considerations.
Audit notice and queries
The audit usually opens with a letter identifying the periods under review and an initial request for records — returns, the general ledger, sales and purchase journals, and source documents for selected transactions. Query letters typically allow about 30 days to respond. The CRA's information-gathering powers under the Excise Tax Act are broad, and refusing to produce records the auditor can otherwise compel rarely helps. The more productive approach is to respond in an organized way while thinking through the legal characterization of each item before it is handed over.
Proposal letter
Before issuing a reassessment, the CRA generally sends a proposal letter setting out the adjustments it intends to make and the basis for each. This is the most consequential stage of the entire process. It is the last clean opportunity to shape the file before an assessment is on the books — to supply replacement documentation, to correct a mischaracterization, and to make legal submissions on the points in dispute. A proposal-letter response that engages the statutory test, rather than simply sending more invoices, frequently moves or removes adjustments that would otherwise be assessed. Proposal-letter deadlines are commonly 30 days.
Notice of (re)assessment
If the proposal-letter response does not resolve the issues, the CRA issues a notice of assessment or reassessment. This starts the 90-day clock for a notice of objection under section 301 of the Excise Tax Act. The assessment also makes the amount legally due — and, importantly, GST/HST collection is generally not restricted while an objection or appeal is pending, a point addressed below.
Notice of objection
A notice of objection must be filed within 90 days of the date of the assessment. The objection moves the file to the CRA's Appeals function, where an officer who was not involved in the audit reviews the assessment afresh. The objection is where the substantive legal arguments are made in full, supported by the documentary record.
Notice of decision and Tax Court appeal
Appeals responds with a notice of decision that confirms, varies, or vacates the assessment. A registrant who disagrees can appeal to the Tax Court of Canada within 90 days of the decision. The Tax Court hears GST/HST appeals under the Informal Procedure where the disputed amount is $50,000 or less per period, and under the General Procedure for larger matters. Our guide on the Tax Court appeal process walks through what the litigation stage involves, and the glossary entry on the notice of objection versus Tax Court appeal compares the two forums.
Documentation: what the CRA expects
Documentation is where many GST/HST audits are won or lost, because so many adjustments are documentation adjustments rather than substantive ones. Two areas dominate.
Input tax credit documentation
Section 169(4) of the Excise Tax Act and the Input Tax Credit Information (GST/HST) Regulations set out exactly what supporting information a registrant must hold to claim an ITC. The requirements scale with the value of the supply. For supplies of $30 or more, the documentation must show the supplier's name (or registered trading name), the supplier's GST/HST registration number, the date, and the amount. For supplies of $150 or more, the registrant must also hold the recipient's name, a description of the supply sufficient to identify it, and the terms relating to the consideration. Missing the supplier's registration number is the single most common reason an ITC is denied, and it is largely curable if a replacement invoice can be obtained from the supplier. The denial mechanics are covered in depth in our companion guide on denied input tax credits and ITC disputes, and the glossary defines the GST/HST input tax credit.
Export and zero-rating documentation
Schedule VI of the Excise Tax Act lists supplies that are zero-rated — taxed at 0% but with full ITC eligibility. For exports of goods, the supplier must hold evidence that the goods actually left Canada: bills of lading showing a destination outside Canada, customs and export declarations, commercial invoices, and carrier confirmations. For services to non-residents under section 7 of Part V of Schedule VI, the supplier must establish that the recipient was non-resident, was not registered for GST/HST, and that the service is not within an excluded category. "We understood it was for export" is not evidence. When zero-rating is challenged, the defence is to reconstruct the documentary record from contracts, communications, and third-party carrier and customs records.
Common adjustments
A handful of reassessment scenarios recur across GST/HST audits:
- ITC denials for insufficient documentation. The largest single category. The credit is denied not because the expense was not incurred, but because the supporting document does not meet the regulatory checklist.
- Zero-rating denials. A supply the registrant treated as a zero-rated export is recharacterized as taxable — often because the recipient was not in fact non-resident, the recipient had a Canadian permanent establishment, or the export evidence does not establish that the goods left Canada.
- Place-of-supply errors. The wrong rate was charged — federal GST at 5% where harmonized HST applied, or HST where only GST applied — because the place-of-supply rules were misapplied. The rules differ by supply type (goods, real property, services, intangibles), and intuition often diverges from the statute.
- Real-property reassessments. New housing or rental rebate clawbacks, self-supply under section 191, substantial-renovation reclassification, and primary-intention disputes. These are addressed in our guide on new housing and rental rebate disputes.
- Section 156 election failures. Two closely related corporations operate as if the nil-consideration election is in place, but the election (Form RC4616) was never properly made or has lapsed because one party stopped being engaged exclusively in commercial activities. GST/HST then applies retroactively to intercorporate supplies, sometimes over several years.
Where a corporation cannot pay a GST/HST reassessment, a parallel assessment of its directors often follows. Under section 323 of the Excise Tax Act — the GST/HST analogue to section 227.1 of the Income Tax Act — directors can be personally liable for unremitted GST/HST. There is a two-year limitation running from the date a person ceased to be a director (subsection 323(5)) and a due-diligence defence (subsection 323(3)). Our overview of director liability for source deductions and GST/HST covers the framework.
The objection route for GST/HST
When an assessment cannot be resolved with the auditor, the formal dispute route runs through the objection and, if necessary, the Tax Court. The mechanics are set out above, but three features of the GST/HST objection process deserve emphasis because they differ from the income-tax experience.
The 90-day objection deadline is firm. An objection filed late requires an application for an extension of time, which is granted only on specific grounds and within an outer limit. The practical lesson is to calendar the deadline from the date of assessment and to file in time.
The objection is a fresh, independent review. The Appeals officer is not the auditor and is not bound by the auditor's view. A well-organized objection that engages the statutory test, with the documentary record assembled and the legal characterization argued, frequently succeeds where back-and-forth with the auditor stalled. Our step-by-step explanation of how to file a notice of objection sets out the process and the deadlines.
Collection is generally not paused. This is the feature that surprises registrants most. For most income-tax debts under objection, the CRA's collection action is restricted while the dispute proceeds. GST/HST is different — the CRA can generally continue to collect a GST/HST assessment even while the objection or appeal is outstanding. That means cash-flow and collections planning has to run in parallel with the substantive dispute, not after it.
Where voluntary disclosure fits
If unremitted GST/HST surfaces that the CRA has not yet contacted the registrant about, the Voluntary Disclosures Program may offer penalty relief and partial interest relief, provided the standard eligibility tests are met — the disclosure must be voluntary, complete, involve a potential penalty, be at least a year overdue, and include payment of the tax. GST/HST disclosures commonly arise where a business operated for years without registering, where tax was charged but not remitted, or where new-housing or self-supply obligations were missed. Because a voluntary disclosure must be made before CRA contact on the matter, the window can close the moment an audit letter arrives. The eligibility tests are explained in our guide on the Voluntary Disclosures Program eligibility.
How Barrett Tax Law approaches a GST/HST audit
Our approach to a GST/HST file follows the structure of the questions the audit actually raises. We confirm the scope — the periods, the supplies, and the ITCs under review. For each disputed supply we reconstruct the legal characterization: taxable, zero-rated, or exempt; the place of supply; the recipient's status; and the supporting documentation. For each disputed ITC we test the documentation against the section 169(4) requirements and obtain replacement documentation where it can be obtained. We look for procedural points, including limitation-period questions under section 298. We frame the response at the proposal-letter stage, escalate to an objection if the proposal response does not move the file, and prepare for the Tax Court where the objection does not resolve the matter. Where a corporation cannot pay, we address the parallel director-liability exposure under section 323 on its own terms, and because GST/HST collection is not paused by an objection, we plan for collections in parallel with the dispute.
If you have received a GST/HST audit letter, a proposal letter, or a reassessment, the most useful first step is to read the document carefully, note every deadline, and preserve the records that answer the questions the CRA is asking. From there, the file can be worked methodically through the stages described above. To discuss a specific GST/HST matter, you are welcome to contact our office for a consultation.