Canada Revenue Agency published a reference guide on business filing and payment deadlines.
The point of the reminder is that business tax deadlines do not all follow one calendar. Income tax, GST/HST, payroll, and instalment obligations can each run on different rules.
For corporations, CRA said income tax instalments are generally required monthly or quarterly when total tax is more than $3,000.
GST/HST deadlines depend on the reporting period. Annual, quarterly, and monthly filers each have different filing and payment schedules, so a business cannot assume that one due date covers all remittances.
CRA also noted that GST/HST annual filers may have to make quarterly instalment payments if net tax is $3,000 or more in both the previous fiscal year and the current fiscal year.
The agency illustrated the instalment point with a business whose 2024 fiscal-year net tax was $4,000 and whose 2025 fiscal-year net tax was expected to be at least that much.