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CRA notices explained

GST/HST notice of assessment

CRA’s assessment of the net tax for one GST/HST reporting period, which confirms the return or changes it.

GST/HST

A plain explanation of a common CRA letter, checked against the Act and CRA’s own guidance.

4 min readUpdated October 4, 2026

The short version

Use these three points first.

01

Each notice covers one reporting period on one GST/HST account.

02

A business has 90 days from the day the notice was sent to object.

03

CRA generally has four years to assess a period’s net tax.

In this guide

What it is

A GST/HST notice of assessment sets out CRA’s assessment of the net tax for a reporting period. It can confirm the return as filed or change it, for example by adjusting input tax credits.

What to check

Dates that matter

Objecting
A person who has been assessed can file a notice of objection within 90 days after the day the notice of assessment was sent.
Assessment period
CRA generally can’t assess a period’s net tax more than four years after the later of the return’s due date and the day it was filed. Misrepresentation, fraud, or a waiver can change that.

What to keep

  • The notice with the GST/HST return for the same period
  • Invoices supporting the input tax credits claimed
  • Proof of payment for the period

In TaxDesk

TaxDesk recognizes a GST/HST notice and files it with the company, beside its GST/HST filings for the period. If CRA then opens a review of the period, track it as an audit matter with the requested items and linked invoices.

See every CRA notice explained

Scope note. This page explains a CRA letter in general terms. It isn’t advice about your situation. Check the letter itself, and confirm the dates and your options with your accountant.

Primary reading

Official starting points used to develop and check this guide.

  1. 01Excise Tax Act, section 298Justice Laws
  2. 02Excise Tax Act, section 301Justice Laws

Continue the workflow

The next useful step

01ReferencesCRA audit letter explainedThe letter or call that starts a CRA audit, setting out when and where it will take place.02ReferencesCRA proposal letter explainedThe letter an auditor sends to explain a proposed reassessment before it is made.

Put the guide into practice

Keep every CRA letter with the record it affects.

TaxDesk reads CRA notices, files them to the right company and year, and keeps them beside the filings and audit matters they relate to.

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