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What a subcontractor invoice must include

A subcontractor invoice needs the usual invoice details, plus a clean split between labour and materials so the CIS deduction lands on the right figure. Miss the split and the contractor can't process the deduction correctly. Here's the full checklist, what to attach, and the answer to the question everyone asks first.

The required details

Every subcontractor invoice should carry the standard elements that make it a valid record:

• Your details — name or business name, address, phone and email.
• The contractor's details — their business name and the site or project the work relates to.
• A unique invoice number — sequential, so nothing is missed or duplicated.
• The invoice date and a due date written in full ("payment due by 30 August").
• A clear description of the work — what you did, where, and over what period.
• Your VAT number, if you're VAT-registered.
• Payment details — how you want to be paid (bank details or a payment link).

The CIS-specific requirements

On top of the basics, a Construction Industry Scheme invoice needs the figures laid out so the deduction is unambiguous:

• Labour on its own line — this is the figure the CIS deduction is taken from.
• Materials on a separate line — materials you paid for directly are not subject to the deduction.
• The CIS deduction shown — 20% if you're registered, 30% if not, applied to labour excluding VAT. Many subcontractors add a "less CIS deduction" line so the net to pay is clear.
• The VAT position — for B2B construction between VAT-registered businesses, the domestic reverse charge usually applies, so you note that the customer accounts for VAT rather than charging it.

What to attach as supporting documents

The invoice is the headline; the backup is what prevents queries. Keep and, where useful, attach:

• Timesheets or a day log to support the labour charge.
• Receipts for materials you're passing on, so the split is defensible.
• Delivery notes or photos for larger jobs.
• The contractor's payment and deduction statements as they arrive — your proof of CIS tax already paid.

Can you pay a subcontractor without an invoice?

Technically a payment can be made without one, but you shouldn't rely on it. Without an invoice there's no clear record of what was charged, no labour-and-materials split for the CIS deduction to work from, and nothing to reconcile against the deduction statement. For anything under CIS, an invoice that splits labour from materials is what lets the contractor deduct the right amount and lets you prove your figures at Self Assessment. If you've been paid without invoicing, raise a matching invoice for your records.