The $30,000 question: registering for GST/HST
What the small-supplier threshold means, when registration becomes mandatory, and why registering early is often the right call.
The rule
If your worldwide taxable revenue stays at or under $30,000 across four consecutive calendar quarters, you are a small supplier and need not register for GST/HST. Cross it and you must register — and start charging — quickly; the timing rules are strict once you exceed the threshold within a single quarter.
Why register early anyway
Registration unlocks input tax credits: the GST/HST on your rent, stock, equipment and software comes back. For any business with real inputs, voluntarily registering below the threshold is usually free money — at the cost of filing returns.
PST is separate
Provincial sales taxes have their own registration rules and thresholds per province — BC, SK, MB and QC each differ. Selling into a PST province can create obligations even from outside it; check the province's rules when you start shipping there.
The threshold is a rolling test, not a calendar one
The small-supplier threshold is measured over consecutive quarters rather than a tidy fiscal year, which is why businesses cross it without noticing: a strong summer can trip it in September for a company whose year ends in December. Once crossed, registration obligations follow quickly.
Watching worldwide taxable revenue as a running figure — rather than checking once a year — is what keeps the crossing planned instead of discovered.
Registering early is often the cheaper answer
Below the threshold, registration is optional — but staying unregistered means paying GST/HST on everything you buy with no way to claim it back. A business investing in inventory, equipment or a fit-out is frequently better off registered from the start, because input tax credits on those purchases are real money.
The trade-off is administrative: registration brings filing obligations and the record-keeping to support them, which is precisely the work a ledger that posts its own tax lines removes.
How SeroBooks applies this
Tax is decided per line, not per invoice. Each line's treatment comes from the product's tax category and the place of supply, so a GST-only item and a GST-plus-provincial item sit on the same sale without anyone thinking about it. Combined rates split into their federal and provincial halves in the ledger — one payable account per tax actually levied — which is what lets a return be filed from the books rather than rebuilt in a spreadsheet.
The Tax report then reads that same ledger for any period: taxable sales by rate with the base for each, zero-rated sales counted rather than dropped, credit notes netted, and a self-check against the sales ledger that says so out loud when the two disagree. Input tax credits accrue from purchase documents as they are entered.
Tax handled per line, per province, automatically.
The place-of-supply engine inside SeroBooks does this all day.