How to File a GST Return Online in Canada: Quick Start Guide — Montreal CPA Firm Near You

Filing your GST return online is one of the most important responsibilities for any Canadian business — yet thousands of entrepreneurs make filing mistakes every year. Some forget deadlines, others miscalculate GST collected, and many incorrectly claim Input Tax Credits (ITCs). Even a small error can trigger penalties, refund delays, and CRA reviews that can freeze your cash flow. Filing your GST return online correctly protects your business, strengthens financial discipline, and builds a permanent defense file in case CRA audits your sales tax compliance. This guide mirrors the exact method used at Mackisen CPA Montreal to file GST returns professionally, accurately, and with full audit protection.

Why Filing GST Online Matters
CRA requires most businesses to file returns electronically through My Business Account. Filing online ensures faster processing, fewer errors, instant confirmation, and the ability to track balances, refunds, and correspondence. Most importantly, it creates a secure electronic trail that protects you if CRA challenges your return or requests additional information.

Legal and Regulatory Framework
GST filing is governed by the Excise Tax Act. Section 238 requires every registrant to file a return for each reporting period, whether tax is payable. Section 225 outlines rules for ITCs. CRA can assess or reassess returns based on available information. Hickman Motors (1997, SCC) established that the taxpayer bears the burden of proving correctness. Canderel (1998, SCC) requires that filings reflect commercial reality and accuracy.

The Cost of Filing Incorrectly
Picture this: You file your GST return manually in your bookkeeping system, assuming everything is correct. Weeks later, you receive a letter from CRA titled “Your GST/HST Return Has Been Selected for Review.” They request invoices, bank statements, proof of payment, contracts, and reconciliation for all ITCs claimed. Your refund is frozen. Your cash flow stops. Until you provide documentation, you cannot access your money. If they find errors, they reassess your return and may charge interest and penalties. This is a common scenario that happens every day — and it is entirely preventable when you file correctly through My Business Account with complete documentation.

Learning Section: Understanding GST Filing Periods
Filing frequency depends on annual taxable revenues:
Under $1.5M: Annual
$1.5M–$6M: Quarterly
Over $6M: Monthly
You may choose to file more often but never less often than CRA requires. Filing more frequently provides better cash flow control and reduces year-end surprises.

SEO Learning: Primary and Secondary Keywords
Primary keywords: how to file GST return, GST return online Canada, CRA GST filing guide, Montreal CPA GST help.
Secondary keywords: GST filing deadlines, GST My Business Account steps, Canadian sales tax return, GST ITC rules.

Step-by-Step Guide: How to File a GST Return Online

Step 1: Log into CRA My Business Account
Use secure login credentials or a Sign-In Partner (bank login). If you have not set up My Business Account yet, complete the registration and wait for the CRA security code.

Step 2: Select Your GST (RT) Program Account
Look for the RT0001 account. Select “File a Return.”

Step 3: Choose the Correct Reporting Period
Ensure the period matches your internal bookkeeping and financial reports. Filing the wrong period is a common and costly mistake.

Step 4: Enter Total Revenue (Line 101)
Enter your total taxable and zero-rated supplies excluding GST.

Step 5: Enter GST Collected (Line 105)
Enter the amount of GST you charged during the period. This must match your sales reports, POS systems, and e-commerce platforms.

Step 6: Enter Input Tax Credits (Line 108)
Claim ITCs based on eligible business expenses. ITCs must be supported by invoices with supplier GST numbers and proof of payment.

Step 7: Calculate Net Tax (Lines 109–113)
CRA will calculate your net tax based on GST collected minus ITCs.

Step 8: Submit Return and Save Confirmation
Download or print the submission confirmation PDF. This is your legal proof of filing.

Step 9: Make Payment or Await Refund
If GST is owing, pay through online banking. If expecting a refund, enable direct deposit for faster processing.

Documentation Section: What You Must Maintain
Invoices with supplier GST numbers
Proof of payment (bank statements, credit card statements, cancelled cheques, e-transfers)
Sales reports from e-commerce and POS platforms
Merchant processor reports (Stripe, Shopify, PayPal, Square)
GST collected and ITC claim worksheets
General ledger and trial balance
CRA filing confirmation PDF
You must keep all records for six years as required by the Excise Tax Act.

Common Mistakes to Avoid
Claiming ITCs without valid invoices
Using credit card slips instead of invoices
Failing to reconcile books before filing
Reporting wrong filing period
Claiming personal expenses as business expenses
Incorrectly coding exempt or zero-rated items
Late filing, which triggers penalties and refund reviews

Winning With Revenue Québec and Canada
Although QST is handled separately, your GST return must still align with your overall financial records. Consistency matters. Mackisen prepares a complete GST package before filing reconciled sales, reconciled ITCs, verified supplier tax numbers, verified business-use ratios, and full audit-ready documentation. This ensures your GST return withstands CRA review and that refunds are processed quickly.

Mackisen Service Hub
Our firm handles GST filings for corporations, freelancers, e-commerce businesses, contractors, and consultants. We reconcile books monthly or quarterly, prepare returns, respond to CRA inquiries, and manage refund reviews. Our team of CPAs and tax lawyers ensures you never face a GST filing alone. We take care of:
Return preparation
CRA My Business Account setup
ITC review
Audit defense
Refund support
Compliance consultation

Why Mackisen
With more than 35 years of combined CPA experience, Mackisen CPA Montreal ensures your GST filing is accurate, complete, and audit-proof. We help you file on time, avoid penalties, manage GST cash flow, and protect your business from CRA reassessments. Whether you are filing your first GST return or managing complex multi-period filings, Mackisen has the expertise to guide you safely and professionally.