What should a mechanic put on an invoice?
A repair invoice should list the diagnostic fee, labor hours at your shop rate, each part supplied, and any sundries or disposal charges. Include the vehicle registration, make, model, and mileage at the time of service, because that record matters for warranty claims and for the owner's service history.
Should I itemize parts separately from labor?
Always. Customers are far more accepting of a large total when they can see that most of it was the part rather than your time. It is also required for warranty purposes, since parts and workmanship are usually guaranteed for different periods, which you should state on the invoice.
Do I need to record the vehicle mileage?
It is worth doing on every invoice. Mileage at the time of service establishes when the work was carried out for warranty purposes, supports the vehicle's service history at resale, and protects you if a customer later claims a repair failed earlier than it did.
Should I give a written estimate before starting work?
Yes, and in many places it is a legal requirement above a certain value, with rules about how much the final bill may exceed the estimate without fresh authorisation. Even where it is not mandated, a written estimate is your best protection against a disputed invoice. Record the customer's approval, ideally in writing, and go back to them if the job grows beyond what was authorised. Customers accept additional work they were consulted about and resist additional work they discover on the bill, which is the entire difference between a repeat customer and a complaint.
How do I explain a large repair bill?
Itemise it. A total of two thousand looks arbitrary; the same total broken into diagnostics, a specific part, labor hours at a stated rate, and disposal reads as a considered piece of work. Note the vehicle registration and mileage, describe the fault and what was done to fix it, and list parts individually where several were replaced. Customers are far more accepting of a large number they can decompose, and an itemised invoice also gives them something concrete to check rather than a figure they can only accept or dispute wholesale.
What should I do with old parts?
Offer to return them, and note on the invoice when they have been returned or declined. Some jurisdictions require the customer to be offered the replaced parts, and even where they do not, offering demonstrates that the work was genuinely carried out. This matters more than it sounds, because suspicion about unnecessary repairs is the most common source of distrust in the trade. Where parts are retained for disposal or core return, record that too, and bill disposal separately so the customer can see what the charge covers rather than encountering an unexplained sundry line.
How should I record warranty information?
State the parts warranty and the labor warranty separately on the invoice, since they usually run for different periods, and record the mileage at the time of service. Mileage establishes when the work was done for warranty purposes and supports the vehicle's service history at resale, which customers value. Keep your copy of the invoice with the job card, because warranty claims frequently arrive months later from a customer who has lost their copy, and being able to produce the record immediately resolves the question and looks considerably better than asking them to prove it.