Anonymised, illustrative composite. An Ontario agent's own trailing four-quarter GST/HST test had already tipped past $30,000 before the quarter that got flagged — three commission cheques had gone out with no tax line on any of them.
At a glance
An Ontario real estate agent, a sole proprietor in their second full year of production, had never registered for GST/HST. Their brokerage's back office had always paid commission cheques net, no tax line, and the agent's own bookkeeping had never flagged a problem — gross commission bounced around from quarter to quarter, some busy, some quiet, and nobody had run the actual test.
The test that matters is not "did I make $30,000 this calendar year." ETA s.148(1) defines a small supplier by the total consideration that became due "in the four calendar quarters immediately preceding the particular calendar quarter" — a rolling four-quarter lookback that decides the following quarter's status before that quarter even opens. Miss that and a quiet stretch can mask a threshold that was already crossed.
The agent's own trailing four quarters, run by their bookkeeper in early October, right after Q3 closed, looked like this:
$30,900 is $900 over the $30,000 small-supplier line. Under s.148(1), that means the agent was not a small supplier for the whole of the following quarter — Q3 2026, July through September — not just from the day the bookkeeper noticed.
Three commission cheques landed inside that same Q3 2026 window, all invoiced the way every prior cheque had been — net, no tax line:
Ontario's combined rate is currently 13% — the federal 5% under ETA s.165(1) plus an 8% provincial component. 13% of $16,325 is $2,122.25: $816.25 of that is the federal share, $1,306.00 the provincial share. None of it sits in a trust account waiting to be remitted — the brokerage paid the cheques as agreed, in full, and the agent spent against them.
Two sections do the actual work once the $30,000 line is behind you. ETA s.240(1) requires registration for “every person who makes a taxable supply in Canada in the course of a commercial activity,” with small suppliers named as the one general exception. Once the trailing-four-quarter test takes that exception away, registration stops being optional.
ETA s.221(1) does the rest: “every person who makes a taxable supply shall, as agent of Her Majesty in right of Canada, collect the tax… payable by the recipient in respect of the supply.” A commission invoice is a taxable supply. Once s.148's trailing-quarter test flips, s.221 doesn't wait for the agent's own bookkeeping to catch up — the collection duty runs from the start of the quarter, whether or not it was ever invoiced that way.
The agent registered retroactively to the start of Q3 2026 and remitted the $2,122.25 out of pocket — nothing to claw back from the brokerage, since the cheques had already cleared and the deals were closed. Going forward the agent is a registrant permanently on this file: every commission invoice from Q4 2026 on carries HST, and the flip side is real — a registrant can claim input tax credits on the HST paid on business expenses, something a small supplier can't do. See also the GST/HST quick method and where commission income lands on a T2125. For a related structuring decision made in the wrong order, see a PREC set up in the wrong order. Purely as an illustration, not a claim about this agent's real expenses: on a hypothetical $500 a month in HST-inclusive marketing and mileage costs, roughly $58 a month of that is now recoverable rather than a sunk cost.
The bookkeeper caught this after one quarter. Run the same average pace — about $5,442 a month in commission — forward another two quarters before anyone reconciles the books, and the uncollected HST grows from $2,122.25 to roughly $6,367 on close to $49,000 of commission, all of it still owed personally and none of it collectable from a brokerage that has already paid out and moved on. The registration test doesn't get easier by ignoring it — the gap between what should have been charged and what actually was just keeps compounding every quarter nobody runs the trailing-four-quarter number.
The tell was sitting in the same spreadsheet the agent already kept — a running twelve-month commission total, never sliced into rolling four-quarter windows. Anyone who re-ran that total on a quarterly rolling basis, rather than a calendar-year one, would have seen Q3 2026 was already going to open below the line two full quarters before the first unregistered invoice went out. The number existed the whole time; it was just never asked the question the Act actually asks.
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