The tax office's list
If you are registered for GST, the document must say 'Tax Invoice', show your business name and ABN, the date, a description of what was supplied, the GST amount (or that the total includes GST), and — for sales of $1,000 or more — the buyer's identity or ABN. Not registered? Then it is an invoice, not a tax invoice, and it must not show GST.
The workshop's list
The tax office does not care which car it was. Your customer, your insurer and the next mechanic do. Every workshop invoice should carry:
- The vehicle: year, make and model.
- The rego — the plate is how everyone finds the car later.
- The odometer reading on the day. It is a point-in-time fact; record it on the document, not just on the car's file.
- Labour itemised with hours and rate, parts itemised with quantity and price, consumables and workshop charges on their own lines.
- What you found and what you recommend — the advisory line that protects you when the customer declines the pads.
- Payment details and terms, and a due date.
One page, and photos
A service invoice should fit on one A4 page. Sections — Labour, Parts, Tyres, Workshop charges — with subtotals make it readable without making it long. If you photographed the worn part and the new one, put the photos on the invoice the customer opens; nothing ends 'was that necessary?' faster.
Keep it findable
Invoices attached to the vehicle, not just the customer, mean the history follows the car. When the owner sells it and the new owner rings you, you can tell them what was done and when. That phone call is a new customer.
Number invoices in one unbroken sequence and never reuse a number. If you issue a credit or a correction, do it as a new document that refers to the old one. An accountant, an auditor or a tribunal reads a gap in the sequence as a missing invoice, and a duplicate number as two documents claiming to be the same sale.