5 Invoicing Mistakes Contractors Make (and How to Fix Them)
Messy numbering, forgotten taxes, follow-ups that never get sent: these mistakes cost time and money. Here's how to fix them.
The L'app du travailleur teamMistake #1: Non-sequential invoice numbers
A lot of contractors start out with a spreadsheet and number their invoices however feels right at the time: "001", then "003", then "Invoice-ClientABC-April"...
As part of your obligation to keep complete records, Revenu Québec expects your invoice numbers to be sequential (1, 2, 3…) and unique. An unexplained gap in the sequence can trigger questions during a tax audit.
The fix: Use a system that generates numbers automatically, or keep a strict log with zero exceptions.
Mistake #2: Forgetting to break out the taxes
If your invoice is over $150 and you're registered for GST/QST, you're required to show the tax amounts separately. Writing "GST and QST included" in the total isn't enough.
Your client needs the separate amounts to claim their input tax credits. If they can't claim them, you'll hear about it.
The fix: Your invoice should always show subtotal, GST, QST, and total, each on its own line.
Mistake #3: Invoicing too late
The best time to send an invoice is the moment the work is done, not the next day, not next week. The same day, ideally before you leave the job site.
Invoices sent within 24 hours of finishing the work get paid on average twice as fast as those sent a week later.
The fix: Send the invoice from your phone before you pack up your tools. The app takes less than two minutes.
Mistake #4: Starting work without a written quote
Doing work without a signed quote sets you up for disputes: "I thought that included the demolition," "You told me a different price"...
A written quote protects both sides. It clearly defines the work included, the price, and, just as important, what's excluded.
The fix: Send a quote before you lift a finger, and get written confirmation from the client. We walk through how to write one and convert it to an invoice.
Mistake #5: Never following up
On average, 30% of invoices aren't paid by the due date. But most late payers aren't acting in bad faith: they simply forgot, or the invoice got buried in their inbox.
A single follow-up at 7 days overdue recovers the vast majority of unpaid invoices. Without one, you're passively waiting on money that's already yours.
The fix: Set up automatic follow-ups. L'app du travailleur sends them on your behalf, on the schedule you choose.
Quick reference
| Mistake | Risk | Fix |
|---|---|---|
| Non-sequential numbers | Tax audit flags | Automatic numbering |
| Taxes not broken out | Non-compliance, unhappy client | Show GST + QST on every line |
| Late invoicing | Slower payment | Invoice same-day |
| No quote | Price disputes | Signed quote before work starts |
| No follow-ups | Money left on the table | Automatic reminders |
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