Tax Software for Ontario Accounting Firms
T1 season pipelines and staggered T2 year-ends tracked on one board.
Tax software for Ontario accounting firms means tracking the work rather than keeping the books: Ontario clients file one 13% HST return, and every corporate file runs a T2 six months after its fiscal year-end with the balance due earlier. SpidNums puts those obligations on one colour-coded board, hosted in Canada.
Combined HST rate in Ontario
CRA
Ontario small-business rate on the first $500,000
TaxTips.ca, 2026
Federal small-business rate on the first $500,000
CRA
Small employer businesses in Ontario
ISED, December 2024
How does tax software work for firms in Ontario?
The CRA administers Ontario's HST — one registration, one return. Ontario clients file a single 13% HST return with the CRA rather than separate federal and provincial sales-tax returns.
Sales tax rarely complicates an Ontario tax engagement: clients file one 13% HST return with the CRA, so the corporate file's sales-tax history lives in the same place as everything else the CRA holds. The complexity in this province is in the corporate calendar, not in the sales-tax regime.
Which CRA deadlines apply?
These rules are federal and apply in every province and territory. Where a due date falls on a weekend or public holiday, the CRA treats the next business day as on time — compute the shifted date each year rather than carrying the calendar forward.
| Filing | Applies to | Filing deadline | Payment | If it is late |
|---|---|---|---|---|
| T1 personal income tax return | Most individuals. | File and pay by April 30 of the following year. Where April 30 falls on a weekend or public holiday, the CRA treats the next business day as on time. | Any balance owing is due April 30. | Late filing costs 5% of the balance owing plus 1% for each full month late, to a maximum of 12 months. Where a late-filing penalty applied in any of the three prior years and the CRA issued a demand to file, the penalty rises to 10% plus 2% per month for up to 20 months. Compound daily interest runs on unpaid balances from May 1. |
| T1 for self-employed individuals | Individuals with self-employment income and their spouses or common-law partners. | File by June 15. The extended filing date applies to the return only. | Any balance owing is still due April 30. Interest accrues from May 1 regardless of the June filing window — this is the single most-missed rule in Canadian personal tax. | The same 5% plus 1% per month structure applies, computed from the June 15 filing date; interest runs from the April 30 payment date. |
| T2 corporation income tax return | Every resident corporation, every tax year, even with no tax payable. | File within six months after the end of the corporation's tax year. Where the year-end is the last day of a month, the return is due the last day of the sixth following month; otherwise it is due the same day of the sixth month. | The balance of tax is due earlier than the return: generally two months after year-end, or three months for eligible Canadian-controlled private corporations claiming the small business deduction. Filing on time is not paying on time. | 5% of the unpaid tax plus 1% per complete month late, to a maximum of 12 months. Repeated failure raises it to 10% plus 2% per month for up to 20 months. |
What is different about running a practice in Ontario?
Four things a firm working Ontario files should be able to state without looking them up. Each is verified against a primary source, linked at the foot of this page.
CPA Ontario is the provincial body; 410,154 of Ontario's 418,322 employer businesses were small businesses as of December 2024.
- Canada's largest market for accounting services — Ontario had 410,154 small employer businesses as of December 2024 — more than Quebec and British Columbia combined. Every one of them is a potential compliance client.
- One 13% HST return — Ontario harmonized its provincial sales tax with the GST, so Ontario businesses charge 13% HST and file one sales-tax return with the CRA instead of two.
- Small-business rate dropping in 2026 — Ontario's provincial small-business rate is 3.2% and falls to 2.2% effective July 1, 2026, which affects year-end planning for corporations straddling that date.
- An Employer Health Tax to watch — Ontario levies an Employer Health Tax on payrolls above an exemption threshold, so Ontario payroll clients carry a provincial obligation on top of CRA source deductions. Confirm the current rate and exemption with the Ontario Ministry of Finance before advising.
Managing tax software across a client book in Ontario
Tax practices lose returns to process, not to preparation: a file waiting on one slip looks identical to a file being worked, and a corporate year-end six months back has a filing date nobody is watching.
A three-partner Mississauga firm with roughly 220 T1 clients and 45 corporate year-ends spread across the calendar never has an off-season. April 30 is the visible crunch, but the quieter risk is the corporate file whose year-end was in September: the T2 is due in March, the balance was due in December, and nothing on a calendar-year spreadsheet says so. Fiscal-year-end-driven reminders are what close that gap.
How SpidNums handles it
SpidNums models the firm as clients, services and work. Assigning a typed service to an Ontario client is what generates the recurring projects, the stages and the reminders — the cadence is recorded once rather than remembered each period.
Every open obligation is then ranked by how close its due date sits and coloured accordingly, so the morning question — what is late, what is close, what is fine — is answered by looking.
- T1 season projects with document-chase, prep and review stages
- Fiscal-year-end-driven T2 reminders at year-end minus one month
- Separate tracking for the filing deadline and the earlier balance-due date
- Kanban or table views per engagement type
- Reminder digests to the assigned preparer
- E-signed engagement letters before work opens
Where this goes wrong
Tax practices rarely fail at the preparation. They fail at the edges of the engagement, where a file is waiting on something and looks exactly like a file being worked.
- The filing date is tracked and the earlier balance-due date is not, so a return filed on time still accrues interest.
- A corporate client's year-end changes and the reminder rule still points at the old month.
- A file stalls waiting on one slip and nobody chases it, because a stalled file and a working file look the same on a desk.
- The June 15 self-employed tail is forgotten after the April push, along with the April 30 payment those clients still owed.
What SpidNums does not do
SpidNums does not prepare or transmit returns. Your T1s and T2s are prepared and EFILEd in your tax software; SpidNums tracks the engagement, the stages, the owners and the deadlines around it.
If your firm already runs a tracking system it trusts, the honest answer is that you do not need this one. The pages on this site are written to help you decide, not to pretend every firm has the same problem.
Tax Software in nearby provinces
Also for Ontario firms
Related guides
Ontario overview
Frequently asked questions
What is the HST rate in Ontario?
Ontario's HST rate is 13%, made up of the 5% federal component and 8% provincially. The CRA administers Ontario's HST — one registration, one return. Ontario clients file a single 13% HST return with the CRA rather than separate federal and provincial sales-tax returns.
What corporate tax rates apply in Ontario?
Ontario's provincial small-business rate is 3.2% on the first $500,000 of active business income, and its general provincial rate is 11.5%. Those sit on top of the federal rates — 9% federally on the first $500,000 and 15% federally on general income. Ontario's small-business rate falls from 3.2% to 2.2% effective July 1, 2026.
How does the software handle staggered corporate year-ends?
The fiscal year-end is stored on the client record and the work is generated from it rather than from the calendar. A year-end-minus-one-month trigger opens the file, and the six-month filing date and the earlier balance-due date are tracked as two separate checkpoints on the same file.
Is client data stored in Canada?
Yes. SpidNums hosts client data in Canada, in the ca-central-1 region, with row-level tenant isolation, an append-only audit log and staff roles that support confidential-client gating.
Does SpidNums prepare or file the return for me?
No. SpidNums does not prepare or transmit returns. T1s and T2s are prepared and EFILEd in your tax software. SpidNums tracks the engagement, the document chase, the stages, the owners and both deadline clocks around it.
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