Start with an honest labour rate
Your labour rate has to cover the technician's wage and on-costs, the rent on the bay, the tooling, insurance, and a margin — before the parts make a cent. Most Australian independents sit somewhere between $120 and $180 an hour depending on the city and the work; specialist and after-hours rates run higher.
Have more than one rate. A standard rate, a lower rate for supervised apprentice work you choose to pass on, and an after-hours rate. Pick the rate per line, not per shop.
Time the job, do not guess it
A 10,000 km service is about an hour of book time; a 40,000 km with a cabin filter and brake inspection closer to ninety minutes. Put the duration on the service in your menu once and let it fill the quote. When your real times drift from the menu, fix the menu — it is the only way the next quote gets better.
Parts at RRP, cost recorded
Every part line needs two numbers: what it cost you and what you sell it for. Sell at recommended retail unless you have a reason not to. Record cost so you can see the margin on the job — and so a supplier price rise shows up in your numbers instead of your bank account.
Consumables — oil, washer fluid, rags, disposal — belong on a Workshop charges line, not buried in labour.
The GST mistake that costs 10%
If you advertise a service at $249 and your system stores $249 then adds GST on the invoice, the customer pays $273.90 and you have a conversation you did not want. Store service prices ex-GST ($226.36 for a $249 service) and let the invoice add 10%. The number on your wall and the number on the invoice match.
If you are not registered for GST — under $75,000 turnover and you have not registered — do not add it at all, and do not call the document a Tax Invoice.
Put it on the menu once
Name, description of what is included, book time, price, interval to the next service and which service comes next. Do that for your dozen most common jobs and pricing becomes picking from a list. The description on the quote is what stops 'I thought that included a wheel alignment'.