How to Do a Construction Invoice (UK Guide)

Construction invoicing in the UK isn’t just “send a bill and hope for the best”. It’s a commercial process tied to your contract, your programme, your valuations, and—crucially—your cashflow. Get it right and you get paid faster. Get it wrong and you’ll spend weeks arguing over variations, retention, VAT, or missing evidence.

This guide explains exactly how to do an invoice for construction (and improve your construction invoicing process) whether you’re a subcontractor, main contractor, or specialist trade.

## What a construction invoice is (and why it’s different) A construction invoice should reflect what you’ve **delivered** on site and what you’re **entitled to be paid** under the contract.

Unlike many industries, construction invoices often need to match:

• Applications for payment / valuations (especially on larger jobs)
• Measured work completed to date
• Variations and compensation events
• Retention (held back and released later)
• Stage payments (milestones)
• Payment notice / pay less notice timelines

If you’re working under a JCT or NEC contract, you may be issuing an application for payment first, then a tax invoice once payment is due/authorised. On smaller domestic works, your invoice might simply follow your quote and agreed stages.

## Before you raise the invoice: check the paperwork Before you create the invoice, confirm three things:

1. Contract terms: payment schedule, valuation dates, retention %, VAT status, and what documents must accompany an invoice.
2. Scope and variations: ensure changes are agreed (or at least evidenced) so you’re not invoicing blind.
3. Site records: delivery tickets, photos, timesheets, sign-off sheets, daily diaries.

Real site example

A drylining subcontractor completes extra fire-stopping around service penetrations after an M&E redesign. If the site team hasn’t logged it properly, that “small extra” becomes a dispute. With a digital trail (photos + variation request + site instruction), the item becomes straightforward to invoice and defend.

SiteSamurai tip: use SiteSamurai to log a Variation with photos, labour hours, and a short description the same day it happens. Later, you can pull that straight into your invoice line items.

## What to include on a construction invoice (UK checklist) A professional construction invoice in the UK should include:

• Your business details: company name, address, phone/email
• Client details: correct legal entity and address (important for main contractors and local authorities)
• Invoice number: unique and sequential
• Invoice date
• Payment due date: aligned with contract terms (e.g., 14/21/30 days)
• Purchase order (PO) number: if required—many contractors won’t process without it
• Project details: site name/address, project reference, package reference
• Description of works: clear, itemised, with dates or valuation period
• Quantity and rates (where relevant)
• Subtotals: net, VAT, gross
• VAT details: VAT number, rate applied, reverse charge if applicable
• Retention: % deducted and net payable
• Bank details: account name, sort code, account number
• Supporting documents: timesheets, delivery notes, signed dayworks, photos, valuation summary

VAT and reverse charge (don’t trip here)

In UK construction, the Domestic Reverse Charge VAT may apply to B2B supplies of construction services. If it applies, you generally don’t charge VAT on the invoice; instead you state that the customer must account for VAT.

Because rules vary by labour/materials and end users, confirm reverse charge status for each client and project. If you’re unsure, get advice from your accountant.

SiteSamurai tip: store each client’s VAT/reverse charge preference in the job setup so your invoice template applies the right wording consistently.

## Choose the right pricing format for your invoice Different jobs suit different invoicing structures. Pick the one that matches the contract.

1) Fixed price (lump sum)

Best for clearly defined scopes.

• Stage/milestone name (e.g., “First fix complete – Plot 12–18”)
• % complete or stage value
• Any agreed variations

2) Schedule of rates / measured works

Common for civils, groundworks, surfacing, brickwork, and framework.

• Item code/description
• Unit (m, m², m³, nr)
• Quantity this period and cumulative quantity
• Rate and value

3) Dayworks

Used when scope can’t be priced upfront.

• Labour: operative names/grades, hours, rates
• Plant: type, hours/days
• Materials: description, quantity, tickets attached
• Signed daywork sheets

Real site example

A small steelwork contractor installs additional goalpost supports due to a late design change. The main contractor instructs dayworks. The steelwork foreman logs labour and plant daily, attaches photos and the signed daywork sheet. When invoiced, the accounts team can process it quickly because it matches the instruction and sign-off.

## Handling retention properly Retention is typically **3–5%**, often split:

• Half released at practical completion
• Half released at end of defects / making good

On your invoice, show:

• Gross value of work
• Retention deducted this period
• Retention held to date
• Net amount due

Practical tip: keep a simple retention tracker per job. Retention is often “lost money” only because it’s forgotten.

SiteSamurai tip: record retention % at project level and let SiteSamurai calculate retention on each invoice, with a clear “retention held to date” line.

## Step-by-step: how to do a construction invoice Use this workflow to keep construction invoicing consistent.

Step 1: Confirm the valuation period and cut-off

Agree what dates you’re invoicing for (e.g., “01–31 March”) and what’s included/excluded.

Step 2: Compile your backup evidence

Gather:

• Signed timesheets/dayworks
• Delivery notes and waste transfer notes (if relevant)
• Site photos (before/after)
• Progress records and QA checklists
• Variation instructions and approvals

Step 3: Build line items that match the job

Write invoice descriptions so they’re recognisable to the QS and accounts team.

Good: “Blockwork to stair core Level 2 – measured to 85m² (Mar valuation)”

Weak: “Building work completed”

Step 4: Apply variations clearly

Separate them into their own section:

• Variation reference
• Brief description
• Date instructed
• Value (or “to be agreed” only if your contract allows)

Step 5: Calculate retention, VAT/reverse charge, and totals

Make it easy for the payer to verify your figures.

Step 6: Add payment details and terms

Include your bank details and state the payment terms exactly as agreed.

Step 7: Send it to the right place (and in the right format)

Many payment delays come from sending invoices to the wrong inbox.

• Confirm the accounts payable email
• Include PO number in subject line
• Attach supporting docs as a single PDF pack where possible

SiteSamurai tip: generate an invoice PDF plus an “evidence pack” (photos, dayworks, delivery notes) directly from the job record. This reduces back-and-forth and speeds approvals.

## A simple construction invoice template structure You can model your invoice like this:

1. Header: business + client details, invoice no., date, due date, PO
2. Project section: site address, project reference, valuation period
3. Works summary:
4. Totals:
5. Payment instructions: bank details and remittance request
6. Attachments list

## Common construction invoicing mistakes (and how to avoid them) ### Missing PO numbers If your client requires a PO, your invoice can sit unpaid for weeks.

Fix: Make PO a mandatory field in your invoice process.

Vague descriptions

QS teams can’t certify what they can’t identify.

Fix: Tie each line to an area, plot, level, or drawing reference.

Invoicing unapproved variations

This triggers pay less notices or outright rejection.

Fix: Log variations in real time and chase written instruction.

Not tracking cumulative values

On measured works, cumulative totals matter.

Fix: Show “this period” and “to date” quantities/values.

Forgetting retention release invoices

Retention often needs its own invoice at the right time.

Fix: Set reminders for practical completion and defects end.

## How SiteSamurai streamlines construction invoicing Construction invoicing improves dramatically when your site records feed your commercial process.

With SiteSamurai you can:

• Capture daily diaries, progress, photos, and deliveries against the job
• Log variations with supporting evidence in real time
• Track labour and plant for dayworks and productivity
• Produce cleaner applications for payment and invoices with consistent templates
• Create a downloadable supporting documents pack to reduce disputes

Real site example: faster approvals

A regional main contractor running a school extension has strict monthly valuation dates. The groundworks subcontractor uses SiteSamurai to attach formation level photos, compaction test results, and signed muck-away tickets to the relevant work items. When the invoice arrives, the QS can certify it quickly because the evidence is already organised—reducing queries and accelerating payment.

## Quick checklist before you hit send - Correct client legal name and site reference - PO number included (if applicable) - Line items match the contract/valuation structure - Variations evidenced and referenced - Retention shown clearly - VAT/reverse charge handled correctly - Bank details correct - Evidence attached ## Final thoughts To do an invoice for construction properly, treat it as part of delivery—not admin. The best construction invoicing is **consistent, evidence-led, and aligned to the contract**. If you capture progress, variations, and dayworks on site as they happen, your invoices become faster to approve and harder to dispute.

If you want to reduce payment delays, start by tightening your site-to-office workflow—then let SiteSamurai pull your records into professional invoices that get you paid on time.