Quote the same day
The first decent quote in usually wins the job. Price it from the van while the scope is fresh - a professional quote sent the same evening beats a better one sent on Thursday. If you cannot price the whole job yet, quote the survey or the first fix and say so.
Itemise labour and materials
A single "supply and fit - £2,400" line invites haggling over the whole number. Separate labour and materials and the customer can see where the money goes, disputes shrink to the line they actually care about, and mid-job changes become priced extras instead of arguments. If you work under CIS, the split is not optional anyway - the deduction only applies to labour, and an unsplit invoice costs you cash flow.
Get it agreed in writing before you start
"Go ahead mate" over the phone is how scope creep starts. Send the quote with an e-signature link and get it accepted before the van is loaded. A signed quote settles what was included when the "while you're here, could you just..." conversations start - and they always start.
Take a deposit on materials-heavy jobs
Boiler swaps, kitchens, rewires - if you are fronting serious materials money, take a deposit that covers it. Sensible customers expect it; the ones who refuse are telling you something useful before you have spent anything.
Invoice the day you finish
Every day between finishing the job and sending the invoice is a day the customer's attention moves on. Invoice from site the day you finish, with a short due date - 7 or 14 days, not 30, unless commercial terms genuinely require it. Put a payment link on the invoice: a customer who can pay by card from their phone tonight pays faster than one who has to remember your sort code at the weekend.
Chase on a schedule, not when you're angry
A polite nudge the day after the due date, another a week later, firmer after that. The trick is that it should not depend on you remembering - set the reminders once and let them go out while you are on the tools. Most late payment is disorganisation, not refusal; a friendly automatic reminder collects it without burning the relationship.
Late payers: know where you stand
When the customer is a business - including a contractor - late payment legislation gives you statutory interest (8% plus the Bank of England base rate) and fixed compensation on overdue invoices. You will rarely want to charge it, but a line in your terms saying you can concentrates minds. With homeowners the lever is different: clear terms up front, a deposit, and staged payments on longer jobs.
Keep the tax lines right
A wrong VAT rate or a missing CIS split gives an accounts department a legitimate reason to sit on your invoice for another month. Right rate, labour and materials separated, your details and payment terms on every document - boring, and exactly what gets you paid on time.