Objecting to a GST/HST assessment

The deadline: 90 days, flat

A GST/HST notice of objection must be filed within 90 days after the day the notice of assessment is sent (ETA s.301(1.1)). There is no individual "later of" rule here — it's 90 days for everyone. Day 0 is the date printed on the notice, and counting starts the day after.

The form: GST159 — not a letter, not T400A

A GST/HST objection must be in the prescribed form: Form GST159. A plain letter is not accepted for GST/HST, and Form T400A (the income-tax objection form) is the wrong form. A well-organised facts-and-reasons summary can accompany the GST159 as a supporting document — but the form itself is mandatory.

Filing: mail it

Mail your GST159 to the Chief of Appeals, Appeals Intake Centre, 1050 Notre Dame Avenue, Sudbury ON P3A 5C1. No fax number is documented for GST/HST objections — don't fax one and assume it was filed. You can also file online: "File a formal dispute" in My Business Account (representatives use Represent a Client).

Separate filings — don't combine

Income-tax and GST/HST disputes are separate filings. If you disagree with both an income-tax assessment and a GST/HST assessment, file each on its own form, on its own timeline. Do not state — or assume — that they can be combined into one objection.

Missed the deadline?

The extension path exists here too: apply to the Minister within one year after the deadline expired (ETA s.303), under the same four-part test — unable to act or genuinely intended to object, just and equitable, applied as soon as circumstances permitted. If refused (or 90 days of silence), apply to the Tax Court of Canada (s.304) within 90 days of the refusal notice. As with income tax: CRA may refuse — urgency, not a safety net.

What a GST/HST objection should cover

• Which assessment(s) and which reporting periods you're disputing;
• per issue: what the CRA decided, the facts as you state them, and the relief you're requesting;
• supporting documentation — sales invoices, purchase invoices with supplier GST/HST numbers, ITC records, books and ledgers for the periods in dispute.

"Specified persons" face a statutory per-issue facts-and-reasons requirement (ETA s.301(1.2)) — but organising it that way is good practice for everyone.