1. The invoice that was never raised
The largest single loss, and the hardest to see, is work that was completed and never billed. It happens at the seams: an emergency attendance that never became a job, a variation agreed verbally, a job closed on a Friday during a busy week.
The only defence is a list: finished jobs with no invoice against them, reviewed weekly by somebody whose job it is to empty it. Companies that introduce this list almost always find money in the first month.
2. Invoicing from memory
Reconstructing a job weeks later produces invoices that are late, approximately right, and impossible to defend when questioned. The parts get rounded, the hours get smoothed, and anything contentious tends to get dropped in the interest of getting it out.
Generating the invoice from the completion record removes the reconstruction entirely and makes every line traceable to something the technician recorded on site.
3. Variations that never reach the invoice
A customer asks for something extra while the technician is there. The technician does it. Nobody writes it down, and it is never charged. This is probably the most common form of margin loss in field service, and it is invisible because nothing went wrong.
Technicians need a way to record an extra, with the customer's agreement captured at the time. It also protects them: an unrecorded extra becomes an argument in which they are the only witness.
4. Descriptions nobody can match
'Service call' as a line item invites a query, particularly in organisations where the person approving is not the person who called. The query costs more in time than the detail would have, and delays payment by weeks.
Describe the work in terms the customer recognises: the equipment, its location, what was wrong, what was done. Reference the job number and the date. Make it matchable to their own record of the visit.
5. No payment instructions
An invoice that states an amount and a due date but not how to pay leaves the customer to find out. Some will ask; many will simply put it aside, and the delay is entirely avoidable.
Payment instructions belong on every invoice: how to pay, where, and what reference to use. If you take payment by bank transfer, the bank details should be on the document rather than in an email somebody has to find.
6. Editing an invoice that was already issued
Changing the figures on an invoice that has gone to a customer creates two versions of the truth, and if payment has been made or part-made, it creates a reconciliation problem that outlives everybody's patience.
The correct treatment is the one accountants use: issue a credit note and a new invoice, so the history reads honestly and both documents can be produced on request. It is also what any auditor will expect to see.
7. Tax treated as an afterthought
Tax rules differ by jurisdiction and by what is being supplied, and the usual failure is applying one treatment to everything because that is what the template does. Equipment supply, labour, subcontracted work and work at different customer locations can all be treated differently.
This is worth getting advice on once rather than guessing repeatedly. Correcting the tax treatment of a year of invoices is expensive, embarrassing in front of customers, and entirely avoidable by asking the question early.
8. Never looking at the ageing
An ageing report : what is outstanding, by how long : takes seconds to read and is the earliest possible warning of a cash problem. Companies in difficulty are frequently companies that were profitable on paper and never looked at their ageing until the bank did.
Read it weekly. The oldest items are the ones least likely to be paid, and the probability falls with every week nobody asks.