Billing a big job in one go at the end means you pay the engineers, subcontractors and expenses for weeks or months before the customer pays you anything. Stage payments for engineering projects fix that: a deposit when the order is placed, then payments as agreed parts of the work are delivered. This guide shows what billing at the end really costs in cash, how to set up deposits and stages your customers will accept, and what to change this week.
Why billing at the end hurts cash flow
On a long job, your costs start on day one. Salaries go out every month, subcontractors invoice as they go, and travel and site costs land on your card. If the only invoice goes out when the final report is issued, you fund the whole job yourself, then wait for your payment terms on top. A 30-day term on a four-month job really means about five months of funding.
It also concentrates risk. If the customer queries one item on a single large invoice, the whole sum can sit unpaid while it is sorted out. With stages, a query holds up one stage, not the whole job. We cover how to keep disputes small in our guide to chasing late payments without damaging relationships.
A worked example: one invoice versus stages
Take a made-up firm, Example Geotechnical Ltd. It wins a 16-week site investigation and design job priced at £96,000. Its costs on the job are £72,000, spread evenly at £4,500 a week. Its terms are 30 days, which we round to four weeks.
Option 1: one invoice at the end
By week 16 the firm has spent £72,000 (16 × £4,500) and received nothing. It invoices £96,000 and is paid around week 20. For the whole job, and four weeks after it, the firm is out of pocket, peaking at £72,000.
Option 2: a deposit and four stages
Now the firm asks for 20% (£19,200) with the order, then invoices 20% at the end of weeks 4, 8, 12 and 16, each paid four weeks later.
- Week 8, just before the week-4 invoice is paid: costs £36,000, received £19,200 (the deposit), gap £16,800.
- Week 12, just before the week-8 invoice is paid: costs £54,000, received £38,400, gap £15,600.
- Week 16, just before the week-12 invoice is paid: costs £72,000, received £57,600, gap £14,400.
- Week 20: the last stage is paid and the full £96,000 is in.
The most the firm is ever out of pocket is about £16,800, against £72,000 with one invoice at the end. That is £55,200 less cash tied up on a single job. Run five jobs like this at once and that could be up to £276,000 (5 × £55,200) less cash tied up, without borrowing anything.
How to set up stage payments for engineering projects
1. Ask for a deposit at order
A deposit does three jobs. It pays for the first weeks of work, it confirms the customer is serious before you book people onto the job, and it tests how quickly their accounts team pays. If a deposit invoice takes six weeks to clear, you have learned something useful before most of the work is done.
There is no set figure. Size it against your early costs: if you have to buy in specialist equipment hire or subcontracted testing in the first month, the deposit should cover most of it. Start work when the deposit is paid, and say so on the quote.
2. Tie stages to things the customer can see
Stages tied to deliverables are easier to agree and harder to dispute than stages tied to dates. “On issue of the desk study”, “on completion of fieldwork”, “on issue of the draft design report” and “on issue of the final report” are all events the customer can check. If the work is likely to slip for reasons outside your control, add a fallback such as “or at the end of month 2, whichever is sooner”, so a customer delay doesn’t become your cash problem.
For long or open-ended work, monthly billing for work done to date is often simpler. It suits time-based work, where you can show the hours behind each invoice.
3. Front-load, don’t back-load
It’s common to see a large final stage tied to “acceptance” or “sign-off”. That final stage is the one most likely to drift, because the customer has what they need. Keep the last payment small, 10% to 20%, and make sure the earlier stages cover your costs as you go.
4. Put the schedule on the quote
The payment schedule belongs on the quote, before the customer says yes, not in an email after the order. Set it out as a short table: stage, trigger, percentage, amount. Our guide to payment terms wording has a sample deposit and stages clause you can adapt.
5. Raise each stage invoice the day the stage is reached
A stage plan only helps if the invoices go out on time. Put the stage triggers in your job plan and make whoever issues the deliverable responsible for telling accounts the same day. In Xero, QuickBooks and Sage you can set up the deposit and stage invoices as drafts when the job starts, so issuing one is a single click.
Do customers have to agree to stage payments?
In most cases this is a commercial negotiation, not a legal right. There is one exception worth knowing about. Under section 109 of the Housing Grants, Construction and Regeneration Act 1996, a party to a construction contract is entitled to instalment, stage or periodic payments unless the work is specified or agreed to last less than 45 days. Section 104 says construction contracts can include design and surveying work, and advice on building and engineering, in relation to construction operations.
So if your firm designs, surveys or advises on construction work, some of your contracts may already carry this right. Whether a particular contract is covered depends on its facts, and there are exclusions. Ask a solicitor before relying on it. We mention it so you know to ask, not as legal advice.
What to say when a customer pushes back
- “We never pay deposits.” Offer a smaller deposit with an earlier first stage, or monthly billing from the start. The aim is to stop funding the whole job, not to win a point.
- “Our system only pays on completion.” Ask whether it pays on completion of a purchase order line. Some purchasing systems can split one order into several lines, one per stage.
- “Your competitors don’t ask for this.” Explain that it lets you hold the team and the dates for them. Customers who are paid in stages themselves are often the easiest to persuade.
If a customer refuses any staging on a long job, treat it as a pricing question. You are lending them the cost of the work, and the price should reflect it.
One thing to check with your accountant: how VAT applies to deposits and stage invoices, since a payment received in advance can affect when VAT is due.
What to do this week
- List your jobs over £20,000 or longer than six weeks from the last year, and note how many were billed in one go at the end.
- For your biggest current job, work out the gap: costs to date minus cash received to date.
- Write a standard stage plan for your most common job type, with a deposit, three or four deliverable-based stages and a small final payment.
- Add the stage table to your quote template, with “work starts on receipt of the deposit”.
- Use it on your next quote, and note which customers accept it without question.
Stage payments are one of the fixes we look at in an Insight review, alongside invoicing speed, chasing and pricing. You can see how a review works, and our free Late Payment Kit includes chase templates you can use alongside a stage plan.
Work out what your billing is costing you
Our free leak calculator takes four numbers and shows how much cash slow invoicing and late payers are holding in your business. If the figure is bigger than you’d like, book a free 30-minute call and we’ll look at where to start.
