gstwatch

The C$30,000 GST/HST threshold has two tests, a 29-day registration clock, and a 6-year memory. gstwatch applies Canada's published small-supplier rules to your quarterly revenue and tells you: are you still a small supplier, when registration takes effect, when you must register by, what filing frequency CRA will assign, and how long to keep records.

Rules verified against Canada.ca, October 2026. Not tax advice — it applies published rules to your numbers and shows its work.

Install

pip install gstwatch

Check the threshold

gstwatch check --quarter 2025-12-31=8000 --quarter 2026-03-31=8000 \
               --quarter 2026-06-30=8000 --quarter 2026-09-30=8000

# or from a CSV: quarter_end,amount
gstwatch check quarters.csv

Both CRA tests are run:

1. Single quarter — one calendar quarter alone over C$30,000: you must charge GST/HST on the supply that takes you over; effective registration is no later than that supply; register within 29 days. Pass --crossing YYYY-MM-DD if you know the exact supply date (otherwise the quarter end is used and the output says so).
2. Four-or-fewer consecutive quarters — total over C$30,000: small-supplier status ends at the end of the month following the quarter in which you crossed; collect from the first supply after that; register within 29 days of that effective date.

Exit codes: 0 still a small supplier, 3 registration required (distinct on purpose, so scripts can branch), 2 usage error. --json for automation.

Filing frequency

gstwatch freq 1400000     # -> annual   (assigned: annual <= C$1.5M)
gstwatch freq 7000000     # -> monthly  (quarterly up to C$6M, monthly above)

Record retention

gstwatch records 2026-05-10   # -> keep records until 2032-12-31

Six years from the end of the year the record relates to.

What's modeled — and what isn't

Modeled: the two threshold tests, 29-day registration clock, effective-date rules (single vs rolling), assigned filing bands, 6-year retention.

Not modeled: the detailed supply inclusions/exclusions (exempt supplies, financial services, capital property, goodwill, associates' rules), voluntary-registration date elections and the one-year minimum, deregistration decisions, and filing obligations themselves. The threshold test includes worldwide taxable supplies (including zero-rated) per CRA's description — bring your accountant for the exclusions.

Sources: when to register and start charging · assigned reporting periods · records to keep

License

MIT-style: use it, ship it, no warranty.