A CRA letter saying it is reviewing a GST/HST return you already filed is usually narrower than it sounds. A GST/HST post-assessment review checks specific amounts on a return the CRA has already processed. The officer wants an explanation and, often, the invoices behind it. A clear, on-time reply with organized records keeps it short.
This guide covers how it differs from a pre-assessment review and an audit, why returns get selected, what the CRA asks for, how and when to respond, and your options if the CRA reassesses.
Table of Contents
- What is a GST/HST post-assessment review?
- Why businesses get selected
- What the CRA typically asks for
- How to respond, and by when
- What happens after the review
- Your objection rights and the GST/HST deadline
- How to prepare your records
- How BBA Tax helps
- Frequently Asked Questions
Key Takeaways
- A GST/HST post-assessment review checks amounts on an already-assessed return. It is not an audit.
- A pre-assessment review happens before a refund is paid. An audit is a deeper examination of your books and records.
- Expect questions about sales, GST/HST collected and input tax credits (ITCs), plus requests for invoices.
- Reply by the date in the letter. You or your representative can upload documents online.
- If the CRA reassesses and you disagree, you have 90 days from the date of the notice of reassessment to file an objection.
What is a GST/HST post-assessment review?
A GST/HST post-assessment review is a CRA check of the amounts on a GST/HST return after the return has been processed. The CRA says it may contact you for a post-assessment review to verify those amounts, ask you to explain what you reported, and request supporting documents such as receipts or invoices. If needed, it adjusts the return.
In its webinar on the post-assessing review, the CRA describes it as a compliance check, not an audit or a books-and-records review. Here is how it compares with the CRA’s other GST/HST checks:
| Pre-assessment review | Post-assessment review | GST/HST audit | |
|---|---|---|---|
| When | Before a refund is approved and paid | After the return has been assessed | After filing, often covering more than one period |
| Why | All refund claims are screened; some are held for a closer look | Amounts that do not line up or carry risk | Risk assessment and random selection |
| Scope | Support for the refund being claimed | Specific lines: sales, tax collected, ITCs | Your books and records in depth |
| Usual result | Refund paid as claimed or adjusted on the notice of assessment | No change, or a notice of reassessment | Proposal letter, then a reassessment if changes are made |
The CRA’s GST/HST audit and examination page explains that every refund request is systematically reviewed before payment, and that returns are picked for audit using both risk assessment and random selection. A review of your income tax return is a separate process; our guide on how to respond to a CRA review or audit letter covers those.
Why businesses get selected
Most reviews start because something on the return does not line up, either with other lines or with information the CRA already holds. Selection does not mean the CRA thinks you did anything wrong.
The CRA compares the revenue, tax collected and ITCs on a return against source data and other revenue lines, for example:
- sales reported against the GST/HST you say you collected;
- sales on your GST/HST returns against business income on your income tax return; and
- ITCs claimed against the size and type of your business.
Common errors the CRA’s webinar mentions include tax collected and ITCs entered on each other’s lines, a missing digit in sales, and net tax entered alone instead of gross tax and ITCs. Zero-rated, exempt or out-of-province sales also tend to draw questions.
What the CRA typically asks for
The CRA usually asks for a short explanation of the amounts in question and the documents that support them. Depending on the issue, the letter may ask about:
- the reason for a discrepancy between lines or between returns;
- your main and other business activities;
- sales made outside your province or outside Canada;
- zero-rated and exempt supplies, or any other sales where you did not collect GST/HST;
- purchase invoices and receipts that support your ITCs; and
- sales records, such as sales invoices, sales reports and the general ledger.
ITCs get the most attention. You can only claim them for GST/HST paid on purchases used in your commercial activities, not for exempt activities or personal use. Each purchase document must also show certain information, and what is required depends on the amount, as set out on the CRA’s input tax credits page:
| Purchase amount | The invoice or receipt must show |
|---|---|
| Under $100 | Supplier’s business or trading name (or an intermediary’s), the invoice date (or date the tax was paid or payable), and the total amount paid or payable |
| $100 to $499.99 | Everything above, plus the supplier’s GST/HST registration number, the total GST/HST charged (or a statement that the price includes it at the applicable rate), and the tax status of each item when taxable and exempt items are mixed |
| $500 or more | Everything above, plus your business name (or your authorized agent’s), a brief description of the goods or services, and the terms of payment |
If an invoice you rely on is missing a required item, such as the supplier’s registration number on a $300 purchase, ask the supplier for a corrected copy before you reply.
Received a GST/HST review letter? BBA Tax can read it with you, pull together the records the officer wants and reply on your behalf. Book a free intro call.
How to respond, and by when
Respond by the date given in the letter, answering each question and sending only the documents requested. The CRA does not publish one standard response period for these reviews, so the date in your letter is the one that counts.
- Confirm the contact is real. Most business mail now arrives in My Business Account, with an email telling you to sign in; otherwise it comes by post. If you get a call, note the officer’s name and any case number and call Business Enquiries at 1-800-959-5525 to confirm it.
- Note the deadline and the reference number. The reference number is usually printed at the top right of the letter. If you cannot get the documents in time, call the officer or the number on the letter before the date passes and ask for more time.
- Prepare a clear package. Answer each question in order in a short cover letter, attach a reconciliation of the return to your books, and name files clearly.
- Submit it. Sign in to your CRA account, go to My Business Account and use Submit documents. Enter the case or reference number, attach your files with a short description and submit. Keep the confirmation number. If you prefer mail, send the package to the address in the letter and quote the reference number.
Using a representative. An accountant you have authorized can deal with the officer and upload the response through Represent a Client.
What happens after the review
The review ends one of two ways: the CRA accepts the return as filed, or it adjusts the return and sends a notice of reassessment. According to the CRA, possible outcomes include:
- no change to your account;
- educational information and filing tips;
- adjustments to your GST/HST return, if required; and
- updates to your business information.
A notice of reassessment shows what changed and any interest or penalties owing. Check it against your own figures, and if a filing error caused the change, fix the process behind it.
Your objection rights and the GST/HST deadline
If you disagree with a GST/HST reassessment, you can file a notice of objection within 90 days from the date of the notice of reassessment. You object to the notice itself. The CRA’s GST/HST objection page notes that you cannot object to a statement of account or an auditor’s proposal letter, so raise disagreements with the officer during the review while the file is still open.
- Online: in My Business Account, select “Register my formal dispute”. You receive a case number to use when you upload supporting documents. Representatives use the same option in Represent a Client.
- On paper: use Form RC592, Notice of Objection, which replaced Form GST159 on October 26, 2026, and mail it to the address shown on the form.
- What to include: each issue you disagree with, your reasons, the relevant facts and your supporting documents.
- Late objections: you can apply for an extension of up to one year after the 90-day deadline, explaining why you could not file on time.
Filing an objection does not stop the CRA from collecting, and interest keeps running on the disputed amount. Paying it limits interest, and if you win the CRA refunds it with interest. If you disagree with the objection decision, you can appeal to the Tax Court of Canada.
How to prepare your records
The best preparation for a GST/HST post-assessment review is a file for each return that ties every line to your books and to source documents you can find quickly.
- Reconcile every return. Tie sales, tax collected and ITCs to the general ledger, and keep a copy of the return with your working papers.
- Check invoices when you enter them. Confirm the supplier’s registration number and the other required details at the $100 and $500 levels before you claim the ITC.
- Document sales without tax. Keep proof of why a sale was zero-rated, exempt or made outside your province, such as shipping records or customer addresses.
- Match your GST/HST sales to your income tax return. Reconcile the year’s GST/HST sales to the revenue on your T1 or T2 and note any difference.
- Keep records long enough. The CRA’s GST/HST records page says to keep them for six years from the end of the year they relate to, longer if an objection or appeal is open. Keep them at your place of business or residence in Canada.
If you find a mistake on a past return before the CRA does, you can correct it with “Adjust a return” in My Business Account. If your books are months behind, our guide to catch-up bookkeeping explains how to get them current.
How BBA Tax helps
BBA Tax is an Ottawa accounting firm led by Karim Bitar, Lead Accountant and ELITE Certified QuickBooks ProAdvisor, with a team that includes bookkeepers. We prepare and reconcile GST/HST returns so each line is backed by the books, and we represent businesses in CRA reviews and audits.
As your authorized representative, we can speak with the officer, gather and check the records, upload the response and, if the CRA reassesses, help you decide whether to object. We meet Ottawa clients in person and work with businesses across Canada remotely.
Want GST/HST returns that hold up to review? Tell us about your business and get a price in about five minutes. Get your instant quote.
Conclusion
A GST/HST post-assessment review is a targeted check of an assessed return, not an audit. Answer by the date in the letter with a clear explanation and the invoices and sales records behind your figures, upload it through My Business Account or your representative, and object within 90 days if you disagree with a reassessment. Reconciled records make every step easier.
Frequently Asked Questions
Is a GST/HST post-assessment review the same as an audit?
No. The CRA describes the post-assessing review as a check of specific amounts on a return it has already assessed, not an audit or a full books-and-records review. An audit looks at your records in much more depth. That said, the review can still lead to a reassessment, so treat the letter seriously and answer it fully.
How long do I have to respond to a GST/HST review letter?
Use the date in the letter. The CRA does not publish a single response period for these reviews, so each letter sets its own. If you need more time or cannot get a document, call the officer or the number on the letter before the deadline and explain why. Do not simply let the date pass.
Can my accountant deal with the CRA for me?
Yes, once they are an authorized representative on your business number. A director or owner can add them in My Business Account under Profile, then Authorized representatives. Your accountant can then speak with the officer, view the letter and upload the response through Represent a Client using the reference number on the letter.
What if a supplier’s invoice is missing their GST/HST number?
For purchases of $100 or more, the supplier’s GST/HST registration number is one of the details you need to support the ITC. Ask the supplier for a corrected invoice that includes it. You can also check that a number is valid with the CRA’s online GST/HST registry before you send your documents.
What is the deadline to object to a GST/HST reassessment?
You have 90 days from the date on the notice of reassessment. You can file online through My Business Account or Represent a Client using “Register my formal dispute”, or on paper with Form RC592. If you miss the deadline, you can ask for an extension within one year after it, with reasons.
Can I still claim ITCs I missed on earlier returns?
Usually, yes. Most registrants can claim an ITC on a later return, as long as it is claimed by the due date of the return for the last reporting period ending within four years after the period it could first have been claimed. The limit is two years for some larger businesses and listed financial institutions.
