Deposits and staged payments: how to bill a long job
On a job that runs for weeks, being paid only at the end means financing the customer's project out of your own account — materials, wages and fuel going out for a month before anything comes in.
A split that customers accept
The most widely accepted shape is a deposit, one or more stage payments, and a balance on completion. Something like:
- Deposit — enough to cover the materials you must buy before starting. Often 25–30%.
- Stage payments — tied to something the customer can see: first fix complete, units delivered, roof watertight. Not to dates, which invite arguments about whose delay it was.
- Final balance — on completion, or on handover.
Tie stages to visible milestones and the conversation is easy: the thing happened, so the payment is due. Tie them to calendar dates and every wet week becomes a negotiation.
Say what happens if a stage is not paid
One line: work pauses until the stage payment clears. It is not aggressive to write it down — it is much less aggressive than downing tools without having mentioned it.
The arithmetic that quietly loses money
Here is the mistake, and almost every spreadsheet makes it. A job is £1,000.00 and you split it 30 / 40 / 30. Each stage is rounded on its own:
- 30% of 1000.00 = 300.00
- 40% of 1000.00 = 400.00
- 30% of 1000.00 = 300.00
That works. Now the job is £999.99:
- 30% = 299.997 → 300.00
- 40% = 399.996 → 400.00
- 30% = 299.997 → 300.00
The three stages sum to £1,000.00. You have just invoiced a penny more than the job. Round the other way and you are a penny short — which, on the final invoice, means the balance never quite reaches zero and the customer's accounts system flags it.
The fix is to allocate rather than round: work out each stage as a running cumulative total, and take each payment as the difference between this cumulative figure and the last. The parts then always sum to the whole, and the odd penny lands somewhere specific instead of appearing from nowhere.
If you are doing this by hand, the practical version is: calculate the first stages, and make the final one the total minus everything already invoiced. Never calculate the last stage as a percentage.
Keep the stages on one document
Each stage invoice should show the whole picture: the contract total, what has been invoiced and paid so far, what this one is for, and what will remain. A customer who can see where they are in the plan pays without asking. One who receives a third invoice with no context asks their accounts department to check it, and that is another two weeks.