Insights
Nov 12, 2025
Mackisen
How to Set Up GST/QST in Your POS System or E-Commerce Platform
Introduction
Whether you operate a boutique store in Montreal or run an online business across Canada, setting up GST (Goods and Services Tax) and QST (Quebec Sales Tax) correctly in your point-of-sale (POS) or e-commerce system is one of the most important steps in running a compliant business. Incorrect setup can cause you to undercharge or overcharge customers, delay refunds, or trigger a tax audit from Revenu Québec (ARQ) or the Canada Revenue Agency (CRA).
At Mackisen CPA Montreal, we’ve helped hundreds of businesses integrate tax-compliant POS and online platforms—from Shopify and Lightspeed to Square, WooCommerce, and custom ERP systems. Our 35+ years of combined CPA and legal experience ensure that every transaction you process automatically applies the correct 5% GST and 9.975% QST, while generating audit-ready documentation.
This guide explains step-by-step how to configure GST and QST in your POS or e-commerce system, what legal rules apply, and how to protect your business from costly errors.
Legal and Regulatory Framework
The obligation to collect and remit GST/QST is mandated by law:
Excise Tax Act (Canada) s.165(1) — requires GST to be applied at 5% on taxable supplies in Canada.
Taxation Act (Quebec) s.255(1) — requires QST to be charged at 9.975% on goods and services sold in Quebec.
Tax Administration Act (Quebec) s.407 — requires all Quebec-based registrants to collect, record, and remit QST accurately.
Excise Tax Act s.280(1) and Tax Administration Act s.59(3) — impose compounded daily interest on unpaid or uncollected taxes.
E-commerce and retail businesses are also subject to digital reporting and cross-agency verification, meaning both CRA and Revenu Québec can electronically verify your POS or online tax configuration during an audit.
Step-by-Step: How to Set Up GST/QST in Your POS or E-Commerce Platform
Confirm Your Registration Numbers
Obtain your GST number (RT) from CRA and your QST number (TQ) from Revenu Québec.
Record them in your POS/e-commerce system under “tax settings.”
Example: GST – 123456789RT0001 / QST – TQ1234567890.
Configure Regional Tax Rates
Set GST at 5% and QST at 9.975%, applied sequentially (QST on price + GST).
Ensure your POS or platform recognizes Quebec as a distinct tax jurisdiction (14.975% combined).
Create Tax Rules by Location
For in-store sales: apply GST + QST automatically for Quebec customers.
For online sales: use “place-of-supply” logic—charge GST/HST or QST based on the customer’s shipping address.
Example: a sale to Ontario = 13% HST; a sale to Alberta = 5% GST only.
Enable Tax Collection in Checkout Settings
Platforms like Shopify, Lightspeed, and WooCommerce have built-in tax modules.
Activate “Automatic Canadian Taxes” and specify Quebec as your home province.
Enter both tax registration numbers under “Business Settings.”
Program Invoice Formatting
Every receipt or invoice must show:
Business name and address.
GST and QST registration numbers.
Itemized prices before and after tax.
Total GST (5%), QST (9.975%), and grand total.
Integrate With Accounting Software
Connect your POS or e-commerce system to QuickBooks, Xero, or Sage to track taxes automatically.
Verify that GST/QST codes are mapped correctly in both systems.
Test and Reconcile
Run sample transactions and confirm:
Taxes are calculated correctly for Quebec and other provinces.
Reports show separate GST and QST collected.
Exempt items (e.g., zero-rated goods) are treated properly.
Jurisprudence and Legal Insight
Canadian courts consistently emphasize that accurate tax collection and reporting are legal obligations:
Canderel Ltd. v. Canada (SCC 1998) — tax filings must reflect commercial reality and correct calculation.
Lac d’Amiante du Québec Ltée (SCC 2001) — confirmed Revenu Québec’s authority to inspect electronic systems for compliance.
Hickman Motors Ltd. v. Canada (SCC 1997) — CRA assessments are presumed valid until proven otherwise by the taxpayer.
These cases make it clear that “system errors” are not valid excuses for under-collection—responsibility always lies with the business owner.
Documentation: Keeping Digital Proof of Compliance
Your POS or e-commerce platform should generate reports showing:
Daily, weekly, and monthly sales totals with GST/QST breakdowns.
Exportable tax summaries for CRA and Revenu Québec filings.
Backup of invoices, receipts, and payment confirmations.
Proof of customer location (for e-commerce “place of supply” verification).
Revenu Québec accepts digital records under Tax Administration Act s.34, provided they’re legible, retrievable, and traceable. Mackisen CPA configures cloud-based storage for clients, ensuring six-year audit compliance automatically.
How CRA and Revenu Québec Audit POS and Online Systems
During an audit, both agencies can request:
Access to your POS/e-commerce reports for the selected period.
Evidence of accurate GST/QST calculation for Quebec customers.
Proof of customer location for interprovincial or cross-border sales.
Integration logs showing when tax rates were last updated.
Revenu Québec’s auditors often test random transactions in your system—if even a small sample shows errors, they can extrapolate liability over years of sales.
Winning With CRA and Revenu Québec
At Mackisen CPA Montreal, we ensure your tax setup withstands every audit. Our 35+ years of experience allow us to combine legal expertise with technical implementation. We:
Audit your existing POS or e-commerce configuration.
Rebuild tax rules for full CRA and Revenu Québec compliance.
Test sample invoices and generate proof reports.
Train your team to handle exemptions, refunds, and tax-free exports correctly.
Represent you during audits and submit documentation directly to authorities.
Mackisen Service Hub: Your Compliance Technology Partner
The Mackisen Service Hub helps retail and e-commerce businesses align technology with tax law. We offer:
GST/QST setup in Shopify, Lightspeed, Square, WooCommerce, and Magento.
System integration with accounting software.
Monthly compliance verification and data reconciliation.
Full audit-ready tax documentation and representation.
Our CPA auditors, tax lawyers, and digital accountants graduates of McGill, Université de Montréal, and Concordia University combine tax knowledge with real-world platform experience.
Real Client Example
A Montreal clothing retailer using Shopify had configured only GST for online orders. Revenu Québec reassessed $48,000 in missing QST plus interest. Mackisen CPA corrected the system, resubmitted amended QST returns, and filed a penalty relief request under Tax Administration Act s.94.1. The reassessment was reduced by 95%, and automated QST collection was implemented permanently.
Why Mackisen
With more than 35 years of combined CPA, legal, and digital integration experience, Mackisen CPA Montreal is Quebec’s trusted expert for GST/QST compliance in retail and e-commerce systems. We don’t just configure your tax settings we make sure your technology, records, and legal obligations work in perfect sync.
When your POS and online systems are configured by Mackisen, every sale is accurate, every invoice is compliant, and every return is audit-ready guaranteed.
