Contractor Invoice Requirements in Canada

A contractor's invoice does two jobs at once. It is a tax document, so it carries everything any Canadian invoice needs. And it is a claim against a contract, so it also has to survive being read by someone deciding whether to release money. The second job is where most invoices fall short.

The fields every contractor invoice needs

• Your legal business name and address — matching what is on the contract, not a trading nickname
• Your GST/HST number — required for your client to claim an input tax credit on anything $100 or over
• A unique invoice number — sequential, never reused
• Invoice date and payment terms — "Net 30" means little without a date to count from
• The client's name and the job site or project — a contractor with several jobs for one client needs the invoice tied to the right one
• A description of the work performed — specific enough that someone who was not on site can match it to the contract
• Subtotal, each tax on its own line, and the total

Progress billing and partial claims

On work billed in stages, the invoice needs to show where this claim sits in the whole. At minimum:

• The total contract value
• What percentage or stage this invoice covers
• What has been billed previously
• What remains

Without that running context, whoever approves payment has to reconstruct it from your earlier invoices — and every reconstruction is a delay.

Holdbacks

Construction legislation in most provinces requires a portion of each payment — commonly 10% — to be held back for a defined period after substantial completion, protecting against liens from subcontractors and suppliers.

Show it explicitly. An invoice that reads "Total $10,000" when the client intends to pay $9,000 creates a discrepancy in both sets of books. An invoice that reads:

...leaves nothing to reconcile, and leaves you a clear record of what is still owed when the holdback period ends.

Change orders — the number one dispute

Work that was verbally agreed on site and never documented is the most common reason a contractor's invoice gets challenged. Bill change-order work as its own clearly labelled line, referencing the date it was authorised and who authorised it. If it was never written down, the invoice is the first written record — and a weak place to be arguing from.

Which sales tax applies to construction work

Construction services generally follow the location of the real property. Work on a building in Ontario carries Ontario HST, whether your shop is in Ontario or not — this differs from ordinary services, which follow the client's address.

If you work across provincial lines, the practical consequence is that the rate can change job to job rather than client to client. Setting the tax per project, not per customer, avoids a whole category of correction.