How to File Your GST/QST Return Online: A Step-by-Step Guide — Montreal CPA Firm Near You

Filing your GST and QST returns online is one of the most important compliance responsibilities for any Quebec business. Whether you’re a freelancer, corporation, e-commerce seller, construction firm, or professional service provider, your GST/QST filings must be accurate and timely. Late filings, miscalculations, or missing documentation can lead to penalties, refund freezes, and even full-scale audits. Many business owners aren’t aware that GST and QST, while similar, are administered by different government bodies — the CRA for GST and Revenue Québec for QST. Making a mistake with either agency can trigger costly consequences. This guide explains how to file both returns online using the exact high-precision method we use at Mackisen CPA Montreal to safeguard our clients from errors, penalties, and audits.

Why Online Filing Matters
Both CRA and Revenue Québec encourage — and in some cases require — electronic filing. Filing online ensures faster processing, fewer errors, instant confirmations, and immediate access to past returns. For refund-heavy businesses, online filing speeds up reimbursement and reduces the risk of manual processing delays. It also creates a digital audit trail that protects you if a tax authority reviews your return.

Legal and Regulatory Framework
GST filing is regulated under the Excise Tax Act, while QST falls under Quebec’s Tax Administration Act. Both laws require businesses to file returns for each reporting period, even if they had no sales. Hickman Motors (1997, SCC) confirms the taxpayer must prove accuracy in filings. Canderel (1998, SCC) requires reports to align with commercial reality. Lac d’Amiante (2001, SCC) gives Revenue Québec authority to reassess returns if documentation is incomplete or inaccurate.

What Happens When You File Incorrectly
Imagine filing your GST/QST return believing everything is correct. Two weeks later, you receive a letter titled “Verification en Cours / Your Return Has Been Selected for Review.” Suddenly CRA or RQ wants invoices, proof of payment, bank statements, contracts, merchant reports, and detailed reconciliation worksheets. Your refund is frozen. Your next filings are flagged. The longer you take to respond, the more your cash flow suffers. If they discover inconsistencies, they can reassess your return, deny credits, impose interest, and open audits for previous years. This scenario is common — and entirely avoidable when you file correctly the first time.

Learning Section: GST vs QST Returns — What’s the Difference?
GST return: Filed with CRA through My Business Account using the GST34 system.
QST return: Filed with Revenue Québec using the FPZ-500-V form through Mon Dossier.
Even though both taxes apply to the same sales, they must be filed separately, paid separately, and reconciled separately.

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Secondary keywords: GST QST reconciliation, Quebec sales tax filing, Montreal CPA GST QST, GST QST penalties.

Step-by-Step Guide: How to File Your GST Return Online (CRA)
Step 1: Log into CRA My Business Account using your secure credentials.
Step 2: Select your GST (RT) account under program accounts.
Step 3: Choose the open reporting period.
Step 4: Enter total taxable revenues excluding GST (Line 101).
Step 5: Enter GST collected on sales (Line 105).
Step 6: Enter Input Tax Credits (Line 108) for GST paid on business expenses.
Step 7: Allow CRA’s system to calculate net tax.
Step 8: Submit the return and save or print the confirmation PDF.
Step 9: Pay GST owing through online banking or wait for your refund.

Step-by-Step Guide: How to File Your QST Return Online (Revenue Québec)
Step 1: Log into Mon Dossier pour les entreprises.
Step 2: Select “File a QST Return – FPZ-500-V.”
Step 3: Enter total sales for the period.
Step 4: Enter QST collected.
Step 5: Enter Input Tax Refunds (ITRs) for QST paid on eligible expenses.
Step 6: Enter adjustments such as credit notes, bad debts, interprovincial self-assessed taxes, or corrections.
Step 7: Review the calculated net QST owing or refund.
Step 8: Submit the return electronically and save the submission receipt.
Step 9: Pay your QST balance or wait for your refund.

Documentation Section: What You Must Maintain for Each Return
All sales invoices showing GST/QST
Purchase invoices with supplier tax numbers
Proof of payment (bank statements, credit card statements, cheques, e-transfers)
Merchant processor summaries (Stripe, Shopify, Square, PayPal)
Reconciliation worksheets
Credit notes and refund documentation
CRA and RQ filing confirmation PDFs
Export and exemption documents for zero-rated supplies
These documents must be kept for six years and presented upon request during audits.

Common Filing Mistakes to Avoid
Using incorrect filing periods
Reporting GST/QST collected that does not match your books
Claiming ITCs or ITRs without proper invoices
Missing proof of payment for claimed expenses
Misunderstanding exempt vs zero-rated supplies
Incorrect QST calculation (not applying QST on GST-inclusive amount)
Failing to self-assess interprovincial or foreign purchases
Not reconciling e-commerce platform reports before filing
Late filing or late payment leading to penalties

Winning With Revenue Québec and Canada: The Mackisen Method
Filing correctly is more than entering numbers into a portal. Mackisen prepares a full compliance package before submitting any return: reconciled ledgers, verified tax codes, validated supplier GST/QST numbers, matched banking and merchant deposits, and complete documentation. This ensures CRA and RQ accept filings without review. We also create GST/QST audit binders so that if your return is reviewed, everything is organized, indexed, and defensible.

Mackisen Service Hub
Our team handles GST and QST filings for corporations, e-commerce sellers, clinics, consultants, trades, and professional service providers. We offer return preparation, portal setup assistance, reconciliation, documentation review, audit defense, and refund management. We ensure every submission meets CRA and RQ expectations and withstands any verification process.

Why Mackisen
With over 35 years of combined CPA experience, Mackisen CPA Montreal ensures your GST and QST returns are filed accurately, on time, and fully supported by documentation. We protect your refunds, prevent penalties, and maintain strong compliance so your business can grow without tax stress.