Invoice on the Day — Every Time
The single most impactful change most plumbers can make to their cash flow is invoicing the same day the job is completed. Every day between job completion and invoicing is a day added to your payment wait — and most plumbers accumulate a backlog of invoices that don't get sent until the weekend, or the end of the month, or "when I get a chance."
The modern solution is job management software that generates invoices directly from your phone on site. When the job is done, tap a button, check the details, and send the invoice before you've left the customer's drive. The customer receives it within minutes while the job is fresh in their mind — not weeks later when they've half-forgotten who you are.
For domestic work, same-day payment is increasingly achievable. Include a payment link in the invoice email — tools like Stripe, SumUp, or GoCardless let customers pay by card or bank transfer instantly. Many customers will pay before you've started your van. This completely eliminates the payment chase cycle.
Setting the Right Payment Terms
Payment terms are the agreed timeframe in which customers must pay. For UK plumbing businesses, the appropriate terms depend on the customer type:
Domestic customers: Payment on completion or within 7 days. There is no reason to give domestic customers 30-day terms — they're not a business managing payment cycles. A 7-day term (or payment on completion) is the standard for domestic plumbing work and customers accept it.
Small commercial customers: 14–30 days. Small business owners manage their own cash flow and 30 days is a reasonable expectation for commercial work.
Larger commercial clients: 30 days is standard; some larger businesses impose 60-day terms. Know your terms before starting work and factor them into your cash flow planning. If a client imposes 60-day terms, your materials and labour costs are funded by you for 60 days — price accordingly.
Include your payment terms on every quote and every invoice. "Payment due within 14 days of invoice date" must be stated explicitly. Vague invoices ("please pay when convenient") produce vague results.
What a Professional Invoice Must Include
A legal invoice in the UK must include specific information. Missing items can delay payment or create disputes:
- Your business name and address (legal name for limited companies, trading name if sole trader)
- Invoice number — Sequential, unique. Necessary for your records and HMRC.
- Invoice date
- Customer's name and address
- Clear description of work done — "Replaced leaking stop valve and repaired pipework at [address]", not just "plumbing work"
- Materials itemised or as a separate line
- Labour hours or fixed price
- VAT number and VAT breakdown (if VAT-registered)
- Total amount due
- Payment terms
- Payment details — Bank account, sort code, or payment link
If you're VAT-registered, all invoices to other VAT-registered businesses must be VAT invoices with a VAT registration number. Domestic customers don't need a formal VAT invoice but including the VAT breakdown is professional and reduces queries.
Following Up on Late Payments
Late payments are a persistent problem in the UK trades. A structured follow-up process prevents them becoming chronic:
Day 1 after due date: Friendly reminder email or text. "Just following up on invoice [number] for £[amount] — payment was due [date]. Happy to help if there's any issue." Many late payments are simply oversight. A prompt, polite reminder usually works.
Day 7: Second reminder, slightly more direct. "I notice invoice [number] is now 7 days overdue. Could you let me know when we can expect payment?" Include the bank details again in case they've lost them.
Day 14: Phone call. A conversation is more effective than another email at this stage. Stay professional but be clear: "I need this resolved by [specific date]."
Day 30+: Late payment statutory notice. Under the Late Payment of Commercial Debts (Interest) Act 1998, businesses can charge 8% above the Bank of England base rate on commercial debts overdue by more than 30 days, plus a fixed £40–£100 compensation charge depending on the debt amount. Mention this in your communication — it often prompts payment.
Final resort: Small Claims Court for amounts under £10,000. Filing a claim via MCOL (Money Claim Online) costs £25–£455 depending on the amount and is a powerful prompt to pay. Many debts are paid the day the court papers arrive.
Getting Paid Before You Start: Deposits
For larger jobs (bathroom installations, boiler replacements, significant pipework projects), taking a deposit before you start is both standard practice and financially prudent. A deposit of 20–40% of the total job value covers your materials cost and reduces the risk of a customer cancelling mid-job or refusing to pay on completion.
Clearly state deposit requirements in your quote and in your terms. "A deposit of [amount] is required to confirm the booking and to fund materials purchase" is straightforward and customers accept it for larger jobs.
For staged jobs, use milestone payments: deposit on confirmation, payment after first-fix completion, final payment on completion. This keeps cash flowing throughout the job and means you're never significantly out of pocket at any stage.