How to Self-Assess QST on Out-of-Province Purchases (Use Tax Obligations) — Montreal CPA

One of the least understood parts of Quebec sales tax law is the obligation to self-assess QST when purchasing goods or services from outside the province. Many businesses believe that if a supplier does not charge QST, then no tax is owed. This is false — and dangerous. Revenue Québec requires businesses to self-assess QST on most out-of-province and international purchases. Failure to do so creates significant audit risk, penalties, interest, and denied Input Tax Refunds (ITRs). This guide explains exactly when, why, and how to self-assess QST using the compliance framework we apply at Mackisen CPA Montreal.

Why Self-Assessment Matters
If a supplier does not charge QST, you may still owe it. Revenue Québec expects you to calculate and remit this tax yourself, then claim an ITR. If you don’t self-assess, RQ can reassess you years later, charging QST plus interest and penalties — even if the supplier was at fault.

Legal and Regulatory Framework
The obligation to self-assess QST is found under the Tax Administration Act, specifically the “use tax” provisions requiring businesses to remit QST on goods and services used in Quebec. This includes interprovincial and foreign purchases. Hickman Motors (1997) reinforces the burden of proof. Lac d’Amiante (2001) confirms RQ’s authority to reassess entire fiscal periods due to missing self-assessment entries.

The Hidden Audit Trap
Imagine buying $80,000 of software from an Alberta supplier who doesn’t charge QST. You assume everything is fine… until Revenue Québec audits you. They discover no QST self-assessment entries for two years. They reassess you for $8,000+ QST, plus interest, plus penalties. You cannot recover the cost because you failed to self-assess at the time of purchase. This is one of the most common — and expensive — audit findings in Quebec.

Learning Section: When You Must Self-Assess QST
When buying goods or services from:
Suppliers in other provinces who do not charge QST
U.S. suppliers (digital or physical goods)
International vendors
Canadian vendors not registered for QST
Digital suppliers offering software, SaaS, or subscriptions
If the product/service is used in Quebec, QST usually applies.

SEO Learning: Primary and Secondary Keywords
Primary: self-assess QST Quebec, QST use tax rules, out-of-province purchase QST.
Secondary: digital service QST rules, Quebec use tax guide, QST self-assessment filing.

How to Self-Assess QST Properly
Step 1: Determine if QST was charged
Step 2: If not, calculate GST (if applicable) and then calculate QST on the GST-inclusive price
Step 3: Record the tax owed as QST payable
Step 4: Enter the ITR (Input Tax Refund) if eligible
Step 5: Include these values in your next FPZ-500-V filing
Example:
Price: $1,000
GST: $50
QST = 9.975% × ($1,000 + $50) = $104.74
You owe $104.74 QST, then claim it back as an ITR.

Documentation Section
Supplier invoice
Proof of payment
Self-assessment calculation worksheet
Reconciliation showing QST payable and ITR
Accounting journal entries
All records must be kept for six years.

Common Mistakes to Avoid
Assuming out-of-province = no tax
Not self-assessing digital subscriptions
Failing to document use in Quebec
Not reversing self-assessment if supplier later charges QST
Claiming ITR without self-assessment entry

Winning With Revenue Québec and Canada
Mackisen reviews your interprovincial and international spending, identifies missing self-assessments, corrects filings, reconciles accounts, and prepares audit-proof documentation to prevent reassessments.

Mackisen Service Hub
We manage QST use-tax reviews, file adjustments, build documentation binders, and handle communication with Revenue Québec.

Why Mackisen
With over 35 years of CPA experience, Mackisen ensures your QST self-assessment is correct, compliant, and fully defensible during audits.