"That looks about right" is not a reconciliation — it's how a rate that drifted, a billing period that ran long, or a fee charged twice gets paid without anyone noticing. The checks that actually catch it are boring, specific, and take less time than the invoice took to generate.
Key takeaways
A rental invoice that's within a few percent of what was expected passes a casual glance every time, because casual glances aren't built to catch small, systematic drift — they catch obviously wrong totals, which is not where most rental billing errors actually live. The errors that cost real money are usually small enough to look plausible and large enough, repeated across every invoice on a long rental, to add up.
Contract rate versus invoiced rate: confirm the daily or monthly rate on the invoice matches what was actually quoted or contracted, not a rate card default the rental company may have applied instead.
Billed period versus days actually on site: rental invoices are commonly billed by calendar days from pickup to return, which can differ from the days the machine was actually being used — confirm the billed period matches the agreed rental window, not an assumed default.
Delivery and pickup fees charged once versus twice: on a multi-invoice rental (common on longer jobs billed monthly), a delivery fee belongs on the first invoice and a pickup fee on the last — not on every invoice in between.
The tax line: confirm GST/HST is charged at the correct rate on the correct base, since the input tax credit formula means an input tax credit can only be claimed on tax genuinely paid on a commercial-activity supply — tax charged on a line it shouldn't apply to, or at an incorrect rate, is a documentable error worth catching before the invoice is paid, not after.
The documentation requirement is not optional, either: subsection 169(4) of the Excise Tax Act requires a registrant to hold sufficient supporting documentation before an input tax credit can be claimed, and for invoices of $100 or more that documentation has to include the supplier's name and their GST/HST registration number, among other prescribed details. Our sister firm's note on what has to appear on an HST invoice covers the same thresholds from the issuing side — a rental invoice missing that registration number is a documentation gap on both ends of the transaction.
Procore’s Commitments tool lets a company “view and filter a detailed list of all the financial commitments (e.g., contracts, purchase order, etc.) on a project,” supports vendor-submitted invoices through the tool directly, and is described as letting a company “easily pinpoint which contracts have been approved or determine the status of invoices and payments” against them — a rental agreement logged as a commitment gets the same visibility as a subcontract or a materials purchase order, rather than being tracked separately (or not tracked at all).
BDC’s own guidance on revenue leakage describes revenue leakage as happening “slowly, month over month,” through “billing errors, missed invoices, untracked change orders, pricing mistakes… or breakdowns in internal processes,” and specifically flags “pricing gaps where… fees don't keep pace with rising supplier costs.” A rental rate that drifted upward from the original quote over a long rental is the same pattern, seen from the paying side rather than the billing side — and it's just as easy to overlook a little at a time.
A damage waiver, fuel surcharge, or environmental/cleaning fee added to a rental invoice is easy to wave through because it looks like a standard line rather than a negotiated one — but the amount and even the existence of these fees is usually set by the rental agreement, not by statute, which means it's checkable against that agreement the same way the rate line is. A damage charge with no corresponding note of what was damaged, or an environmental fee larger than what the same rental company charged on the last job, is worth a call before it's paid, not after.
The same logic applies to a fuel surcharge: confirm it against the actual fuel level noted at pickup and return, not against a flat assumption that the surcharge is standard and therefore correct.
A reconciliation that only happens when someone happens to have time catches errors inconsistently — the fix that actually holds is attaching the four-line check to the approval step itself, so an invoice can't move to payment without it being run. That's a smaller process change than a full audit of every past invoice, and it stops new drift from accumulating while any backlog of older invoices gets reviewed separately.
A worked example
A monthly-billed equipment rental was quoted at $4,200.00 a month. Three invoices in, the rate on the invoice has crept to $4,450.00 — a $250.00 monthly gap that, unnoticed, would run $3,000.00 a year on this one piece of equipment alone if the rental continued at that pace.
Separately, the first invoice correctly carries a $180.00 delivery fee, but the second invoice also carries an $180.00 delivery fee, which shouldn't recur until the equipment is actually picked up at the end of the rental. That's a second, distinct $180.00 error caught by the same four-line check, on the same invoice run.
Neither error is large enough to fail a casual glance at the total. Both are caught by checking the specific rate line against the original quote and the fee lines against the rental's actual pickup/return events — the two checks that matter, run in a few minutes against the commitment record.
Compare the invoiced daily or monthly rate against the original quote, line by line — that single check catches the most common and most expensive drift, and takes less time than reviewing the whole invoice in detail.
Yes — Excise Tax Act section 232 exists for exactly this: when consideration for a supply is reduced after the fact, a credit note (or debit note) adjusts both sides' net tax for the period, and the returns-and-credits article covers the same mechanism for a return or overcharge more generally.
Logging it as a commitment against a purchase order or subcontract — the way Procore’s Commitments tool treats it — gives it the same visibility and approval trail materials already get, rather than letting rental invoices arrive and get paid outside the process that catches errors on everything else.
Whoever owns the commitment record for that rental — typically the project manager or a dedicated accounts-payable reviewer with visibility into the original agreement — rather than whoever happens to process invoices for payment generally. Reconciliation depends on knowing what was actually agreed, not just what the invoice says.
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