“It’s £8,400… or £7,600 for cash.” Every homeowner meets this offer eventually, and the arithmetic looks friendly. It isn’t, because what’s actually being sold is not a discount but a swap: money off now in exchange for every protection you’d want later. Worth understanding precisely before you decide.

Paying cash is not illegal, for you or the trade. Tax on the income is entirely the trader’s obligation, a homeowner has no duty to police it (the CIS tax-deduction rules that apply in construction bind contractors, not private householders). The trouble isn’t legality. It’s what the cash deal does to your position, and what it tells you about the business you’re dealing with.

What you give up

  • The paper trail. No invoice, no receipt, often no written quote, so when the work fails, proving what was agreed, what was paid and even who did the work becomes your word against theirs. Every remedy in our dispute guides runs on documents; cash jobs generate none.
  • Your consumer rights, practically speaking. The Consumer Rights Act still applies in theory, but enforcing “reasonable care and skill” against someone with no paperwork, no fixed address on anything, and payments that officially never happened is close to hopeless in practice.
  • Section 75 and chargeback, card protections obviously never attach to notes in an envelope.
  • Warranties and guarantees. Manufacturer warranties want proof of professional installation; insurance-backed guarantees want the job to exist on paper. A cash boiler swap can quietly void the warranty and skip the Gas Safe notification that should follow it.
  • The building control trail. Notifiable work (electrics, heating, structural) done off the books is disproportionately likely to skip certification, a problem that surfaces when you sell.
  • Your evidence you paid at all. If the relationship sours mid-job, you cannot prove the £4,000 handed over in tenners. This cuts both ways and ugly disputes have turned on exactly this.

What it tells you

A business that runs on undeclared cash is showing you its attitude to rules generally, insurance kept current, building regs notifications, the contract you asked for. Not always; the semi-retired decorator doing small jobs for neighbours is a different animal from an outfit taking £30,000 extensions in cash. But the correlation is real, and vetting exists precisely to sort one from the other.

Where cash is honestly fine

Small, low-stakes, self-contained jobs: the £80 gate repair, the £150 garden tidy, odd jobs where nothing can meaningfully fail later. Even then, a text saying “thanks, £150 received for X” costs nothing and creates the receipt. The risk scales with the money and the failure modes: rewiring, gas, structure and waterproofing are the last places on earth for an undocumented deal.

The VAT reality check

Much of the “cash discount” is simply the VAT not being charged, which only exists as a saving where the trader is VAT-registered (compulsory above £90,000 turnover) and was going to charge it. Many sole traders legitimately sit under the threshold: their price has no VAT in it anyway, by bank transfer, with an invoice. So before trading away your protections for 20%, ask the simpler question, “are you VAT-registered?”, and see our VAT on renovations guide for the schemes that reduce VAT lawfully. Pay by bank transfer against an invoice, keep everything, and let the discount conversation be about scope and timing instead.