CIS Invoices on WhatsApp — UK Subcontractor Guide
CIS is the most common reason a subcontractor's invoice gets bounced back. This guide walks through the rules — 20% on labour, never on materials, plus the reverse-charge VAT wording that applies on most VAT-registered construction work — with worked examples and exactly what should appear on the invoice.
If you subcontract on UK construction work, your invoices have to reflect the Construction Industry Scheme (CIS) correctly — and the rules trip up a lot of self-employed tradespeople. The most common mistake is applying the 20% deduction to the whole invoice, including materials. This guide explains the rules, the wording, and how to send a compliant CIS invoice from WhatsApp in 60 seconds.
The one rule that matters: 20% on labour, never on materials
Under CIS, registered contractors deduct tax at source from payments to subcontractors. For most subcontractors the deduction is 20% — but it applies only to the labour element of the invoice, not the materials. Materials, plant hire, fuel for plant, and CITB levy are all paid gross (no deduction).
A worked CIS invoice example
You're a subcontract plumber working on a new-build site. The job: install heating system, £1,200 labour and £480 materials. You're VAT-registered, the main contractor is VAT-registered (so reverse-charge VAT applies — see below).
- Labour: £1,200.00
- Materials: £480.00
- Subtotal: £1,680.00
- VAT: reverse-charge (you don't add VAT — the contractor accounts for it)
- CIS deduction (20% on labour only): -£240.00
- Net payable to subcontractor: £1,440.00
The contractor pays you £1,440 directly. They report the £240 CIS deduction to HMRC against your UTR. You see the deduction credited against your eventual Self Assessment tax bill.
Reverse-charge VAT — when it applies
Since 1 March 2021, most B2B construction services in the UK use the VAT reverse charge instead of the subcontractor charging VAT. The reverse charge applies when both parties are VAT-registered, the work is reportable under CIS, the customer is not the end-user, and the supplier isn't an employment business.
On the invoice, you don't add VAT. Instead, you include wording like: "Reverse charge: customer to pay VAT to HMRC." Then you note the VAT rate (usually 20%) and the VAT amount that would have applied. The customer accounts for both the input and output VAT on their own return.
What every CIS subcontractor invoice should include
- Your business name, address, and contact details
- Your Unique Taxpayer Reference (UTR) — the contractor needs this to file the CIS return
- Your trade registration where relevant (Gas Safe, NICEIC, NAPIT, ELECSA, SELECT)
- Invoice number and date
- Contractor's name and address
- Description of the work and site address
- Labour total — clearly labelled, separate from materials
- Materials total — clearly labelled, separate from labour
- CIS deduction amount (20% of labour for standard registered subcontractors)
- Net amount payable after deduction
- Reverse-charge VAT wording if applicable
- Your payment details (sort code and account number, or a Stripe payment link)
Sending CIS invoices on WhatsApp
The fastest way to send a compliant CIS invoice is to describe the job to Wedge in plain English: "CIS invoice to ABC Construction for the heating install at 14 Acacia Avenue. £1,200 labour, £480 materials. Reverse-charge VAT." Wedge calculates the 20% deduction on labour only, applies reverse-charge VAT wording, prints your UTR and trade registration in the footer, and generates a branded PDF that lands in the contractor's inbox in under 60 seconds.
Run the numbers yourself with our free CIS invoice calculator — same logic, no sign-up required.
Try the free CIS invoice calculator
Enter labour and materials, get the correct HMRC deduction and net payable.
Higher-rate (30%) CIS deduction — when it applies
If you're not registered with HMRC for CIS, the contractor deducts 30% from your labour instead of 20%. The fix is to register on the HMRC site (it takes about 10 minutes). Once you're on the system, your status drops to standard 20%, and after a track record of compliant returns you can apply for gross payment status (no deduction at all).
What about gross payment status?
Gross payment status means the contractor pays you in full with no CIS deduction at source. You're responsible for paying the full tax yourself through Self Assessment. To qualify you need to meet HMRC's compliance, turnover, and business tests — broadly, demonstrate that you're a properly established UK construction business with a clean tax record. Worth applying for if you turn over £30,000+ annually as a subcontractor: the cash-flow improvement is significant.
Try CIS invoicing on WhatsApp free
Send compliant CIS invoices via WhatsApp in 60 seconds. Free forever; 1% only when paid (capped £50). Reverse-charge VAT, materials/labour split, UTR and trade registration handled automatically.
