A contractor invoice template with HST and e-Transfer where they belong.

If you are registered for GST/HST, the CRA requires your registration number on invoices above a small threshold so your client can claim input tax credits. Put it on every invoice and you never have to think about the threshold. This is general information, not tax advice.

HST in Ontario, New Brunswick, Nova Scotia, PEI and Newfoundland and Labrador; GST plus PST in BC, Manitoba and Saskatchewan; GST plus QST in Quebec; GST alone in Alberta and the territories. Whether PST applies to labour or only materials varies — ask your accountant. Rates by province.

Invoice the full amount, then deduct the deposit on the “less payments received” line so the balance due is what the client actually sends. The client's records and yours then match.

If the contract retains a holdback, deduct it on each progress invoice and bill it as a final holdback-release invoice once the lien period has passed. The template has the line; the contract sets the percentage.

You can state one in the terms, and courts generally enforce reasonable interest that was agreed in advance. Put it in the contract and repeat it on the invoice; do not spring it on a client afterwards.