Tradesman Invoice Template: VAT, CIS and Reminder Wording Drafted With AI

A tradesman's invoice needs a unique number, both parties' details, the invoice and supply dates, a clear description, the amounts and the total owed, plus VAT where you charge it. Subcontractors under the Construction Industry Scheme (CIS) also split labour from materials. AI drafts the wording and reminders; your accountant checks the VAT and CIS lines.

Most AI errors on trade invoices are not spelling slips. They are tax lines the tool was never told about: VAT added to a reverse-charge invoice, a CIS deduction taken from materials, or a VAT number invented to fill a gap. The working split is simple. Your invoicing software or bookkeeping supplies every figure and status, AI writes the descriptions, the terms and the reminders, and you check the lines against a short list before anything is sent.

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Nine fields on every invoice, and the extra ones VAT adds

The official guidance lists nine items that every invoice needs. The table adds who should fill each one, because that split decides where AI helps and where it only gets in the way.

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A VAT-registered tradesman invoicing another VAT-registered business must issue a full VAT invoice. That adds your VAT registration number, the time of supply and the date of issue, the quantity or extent of the work, the VAT rate with the amount payable excluding VAT, the total VAT chargeable, the unit price and any cash discount rate. Invoice numbers must run in sequence from one or more series; how to treat a number you cancel is one of the questions for your accountant at the end. A householder is a different case: the guidance says you need not issue a full VAT invoice to a customer who is not VAT-registered, though a retail customer who asks for one should get it. Most registered traders still show the VAT line and their VAT number on every invoice, because the customer can then see what they paid and nobody has to reissue anything. You cannot charge VAT until you are registered.

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One bathroom refit, three invoices: no VAT, VAT and reverse charge

The same job produces three different invoices depending on who sends it and who receives it. Take a bathroom refit with 1,800.00 of labour and 640.00 of materials that the tradesman bought. All amounts are in pounds and illustrative, and VAT is shown at the standard rate of 20%. Invoice A comes from a tradesman who is not VAT-registered, billing a householder.

INVOICE 0147
Invoice date: [date]          Supply date: [date work finished]
From: [your name and trading name], [address], [phone], [email]
To: [customer name], [customer address]

Bathroom refit at [job address]
  Labour: strip out, first-fix plumbing, tiling, fit-out      1,800.00
  Materials supplied by us (receipts held)                      640.00
                                                 Total due    2,440.00

Payment due within 14 days of the invoice date.
Bank transfer: [account details]

Invoice B is the same job from a VAT-registered tradesman. It adds the VAT number and two lines, and the total rises by the VAT.

INVOICE 0148
VAT registration number: [number]
...
  Labour: strip out, first-fix plumbing, tiling, fit-out      1,800.00
  Materials supplied by us (receipts held)                      640.00
  Net total                                                   2,440.00
  VAT at 20%                                                    488.00
                                                 Total due    2,928.00

Invoice C goes from a VAT-registered subcontractor to a VAT-registered contractor whose payments to subcontractors fall under CIS. Here the reverse charge applies, which means the customer, not you, accounts for the VAT. The official guidance says the invoice must still show everything a VAT invoice requires, carry a note making clear that the reverse charge applies, and state how much VAT is due under it (or the VAT rate, if the amount cannot be shown) without adding that VAT to the amount charged.

INVOICE 0149
VAT registration number: [number]
To: [contractor business name], [address]
...
  Labour                                                      1,800.00
  Materials supplied by us (receipts held)                      640.00
  Total excluding VAT                                         2,440.00

Reverse charge: customer to pay the VAT to the tax authority.
VAT due under the reverse charge at 20%: 488.00 (not added to this invoice)
                                      Total payable to us    2,440.00

CIS (optional line): expected deduction, 20% of labour 1,800.00 = 360.00
Expected payment after deduction: 2,080.00

The wording of the reverse-charge note is not mine to improvise. The guidance gives its own examples, which cite the section of the VAT Act that creates the charge, and says the invoice must include the reference "reverse charge". Copy the wording your accountant gives you.

The three differ in three places: the VAT line, the reverse-charge note and the CIS line. The 360.00 that the contractor withholds in column C is not a loss. The contractor pays it to the tax authority on your behalf, and it counts towards your own tax bill. The VAT rate used here is the standard one; other rates apply to some kinds of work, so your accountant confirms which applies to each job type you do.

Here is how the commonest error shows up in practice. A tradesman asks an assistant to "make the invoice for the bathroom job" and pastes the totals, without saying the customer is a contractor on the reverse charge. The tool does what most invoice templates do and adds VAT at 20%, so the invoice reads 2,928.00. The contractor's bookkeeper, who is meant to account for that VAT, rejects it and asks for a corrected invoice. The tradesman issues a credit note and a new invoice, and the payment waits for both. The fix sits upstream: the prompt states the customer type, and the final check asks whether there is any VAT in the total.

Which of the three invoices applies to this customer?

AI cannot answer this, because it only sees what you paste. It does not know your VAT status, whether the customer is a CIS contractor, or whether the customer has told you in writing that it is an end user. Settle it per customer, once, with this table.

Ask each new business customer for its status in writing and file the reply next to the customer record. It takes two minutes at the start of a relationship and spares you a disputed invoice six months in. The services the reverse charge covers follow the CIS list of construction operations, which includes installing heating, drainage and fire protection systems, repairs and alterations, and scaffolding, and which excludes items such as architects' work. Check the trade you are in rather than assuming.

A prompt that writes the lines and leaves the arithmetic alone

Use AI for the descriptions, the terms paragraph and the tone. Keep the figures out of its hands, since chat assistants make arithmetic slips that look convincing. The tutorial on why AI is bad at maths explains the pattern. Here is a prompt that enforces the split.

Write invoice line descriptions and a short payment-terms paragraph from my job notes. Do not calculate anything.
Every amount, my VAT status, any VAT number and any reverse-charge note come from me; if I have not given one, write [TO COMPLETE]. Do not add a VAT line unless I say VAT applies. Mark anything you assumed with [ASSUMED]. Use plain English a householder would follow.

Job notes: ripped out old suite and tiles, new bath and basin, first-fix plumbing, tiled walls and floor, new extractor fan fitted by the electrician (not us), four days on site, finished on [date].
Terms: payment within 14 days of the invoice date by bank transfer.
Customer type: householder. I am not VAT-registered.

A typical reply gives a few clean description lines, a terms paragraph and some extras you did not ask for. Illustratively, it might read:

1. Strip out existing bathroom suite and wall and floor tiles; remove waste.
2. Supply and fit new bath and basin; first-fix plumbing.
3. Supply and fit wall and floor tiles.
4. Supply and fit extractor fan (electrical connection by others).
Amounts: [TO COMPLETE]
Payment is due on receipt of this invoice. VAT is included in the total. All work is guaranteed for 12 months.

Four things need fixing before it is usable. Line 4 bills for an extractor fan that your notes say the electrician fitted, so it comes out. "Due on receipt" contradicts the 14 days you specified. "VAT is included" is wrong for a trader who is not registered, and printing it can imply a charge that does not exist. "Guaranteed for 12 months" is a promise you never made, and a promise on an invoice is one you may have to honour. Delete all four. The other description lines are good, and the [TO COMPLETE] marker shows the model followed the rule about figures.

Paste the job lines, never the customer's name or address, and replace both with "the customer" in the prompt. The assistant does not need them, and once the text is in an invoicing app the details are merged in anyway. A ChatGPT Project or a Claude Project holding this instruction means each invoice starts from the same rules.

Before and after, for the descriptions alone. The notes on the job sheet read: "bath out, new in, taps, tile 2 walls, sealed". The version worth sending says: "Remove existing bath. Supply and fit new bath with taps. Tile two walls around the bath, including sealing." A customer who queries the total can follow the second one, and the first invites an argument about what was included.

Where the CIS deduction comes from and how to check a statement

Under CIS the contractor deducts a percentage from your payment and passes it to the tax authority. The official guidance gives three rates: 20% if you are a registered subcontractor, 30% if you are not registered, and 0% if you hold gross payment status. The deduction counts as an advance payment towards your own tax bill, so it is money moved, not money lost.

The base matters more than the rate. The contractor starts from your invoice total and takes off the VAT, then the cost of materials you paid for directly, plant hire, fuel used (except for travelling), consumable stores and the cost of manufacturing or prefabricating materials. The rate is applied to what is left. That is why Invoice C keeps labour and materials on separate lines, and why you keep the receipts. If you paid for materials directly and cannot show receipts, the contractor estimates their cost, so keep the receipts.

Labour-only work is simpler. A plasterer invoicing 1,500.00 for labour, with no materials or other costs to remove, has 20% of the whole 1,500.00 deducted, which is 300.00, and receives 1,200.00. With gross payment status the deduction is 0% and the full 1,500.00 arrives.

The contractor must give you a payment and deduction statement within 14 days of the end of each tax month. A tax month runs from the 6th to the 5th, so for 6 May to 5 June the statement is due by 19 June. Reconcile each one against your own invoice. Take Invoice C. The correct deduction is 20% of 1,800.00, which is 360.00. If the statement shows 488.00, the contractor has taken 20% of the whole 2,440.00, materials included, and you are 128.00 short. Send the receipts for the 640.00 of materials and ask for a corrected statement. If the statement shows 30% instead, the contractor treats you as unregistered, and that is a registration question to settle before the next payment: 30% of 1,800.00 would be 540.00.

The series has more on this in the tutorials on a CIS deduction statement template and the CIS monthly return, which covers the contractor's side.

Late-payment terms: what the interest rules actually give you

The statutory late-payment rules are for business debts. The official guidance frames them as one business claiming from another that pays late for goods or services, so they suit a slow-paying contractor and are not the tool for a householder. If no payment date was agreed, a payment is late 30 days after the customer receives the invoice or after you deliver the work, whichever is later. An agreed date for a business transaction must usually fall within 60 days.

Interest runs at 8% a year above the base rate for business-to-business transactions. Work it out as the annual interest divided by 365, multiplied by the days late. On top of interest you can claim a fixed sum per late payment: 40 pounds for debts up to 999.99, 70 pounds from 1,000 to 9,999.99, and 100 pounds at 10,000 or more, charged once per payment. A different interest rate in a contract replaces the statutory one, so make sure your terms and any customer contract agree before you quote it.

A quick sum shows the scale. Suppose a business customer owes an invoice of 3,000.00 and pays 30 days late, and assume the base rate is 4% (look up the current figure). Annual interest at 12% is 360.00, so 30 days costs 3,000 × 0.12 ÷ 365 × 30 = 29.59. The fixed sum for a debt in the 1,000 to 9,999.99 band is 70 pounds. The claim is 99.59 in total. That is real money for a small firm, and small enough that a firm reminder is a sensible first step before any claim.

AI can draft the footer wording once you tell it who the customer is. Two versions cover most trades:

Business customer:
Payment is due within 14 days of the invoice date. If payment is late, we may charge interest and recovery costs under the statutory late-payment rules for business debts, unless a different rate is set out in our contract.

Householder:
Payment is due within 14 days of the invoice date. If you expect a problem, please tell me before the due date and we can agree a new one.

Have your accountant or solicitor read the business version once, then freeze it. For households, the second version does more good than any threat, because a customer who has a cash-flow problem and can talk to you pays sooner than one who is frightened of you.

A reminder sequence, drafted by AI and checked by you

Five messages cover most unpaid invoices, and each gets firmer without getting rude. Counting from the due date as day 0:

Step 2 works best as a text, and a short one beats a polished one. Ask the assistant for "two sentences, no apology, no pressure" and expect something close to this:

Hi [first name], quick check that invoice [NUMBER] for [AMOUNT] reached you. The bank details are on it. Thanks, [your name]

Give the assistant the step, the facts and the limits, and ask for one short message. Here is a request for step 3:

Write reminder 3 for an unpaid invoice. Tone: friendly but direct, no threats, no sarcasm. Invoice [NUMBER] for [AMOUNT], due on [DUE DATE], now 7 days overdue. Ask for a payment date by [DATE]. Mention bank details are on the attached invoice. Customer is a householder. One short paragraph, sign off with [your name], greeting uses [first name]. Do not mention interest, fees or legal action. Mark anything you assumed with [ASSUMED].

An illustrative first draft:

Hi [first name], I'm following up on invoice [NUMBER] for [AMOUNT], which was due on [DUE DATE]. I'm sure this is just an oversight, and it is now ten days overdue. Could you let me know by [DATE] when I can expect payment? The bank details are on the attached invoice. Thanks, [your name]

Two repairs are needed. The draft says "ten days overdue" when it is seven, a small slip that makes the customer doubt your records. And "I'm sure this is just an oversight" can read as presumptuous to someone who disputes the bill; replace it with "a quick check that this reached you". Then drop the figure of days altogether and quote only the due date, which is a fact you hold.

Step 4 is where business and household customers part company. For a contractor who has missed the date, the message can say: "Invoice [NUMBER] for [AMOUNT], due on [DUE DATE], remains unpaid. Under our terms we may charge interest and recovery costs under the statutory late-payment rules. Please pay by [DATE], or tell me by then if you have a query on the invoice." Check before sending that your contract does not set a different rate, since that rate would then apply. Never send this wording to a householder.

If a customer disputes one line, do not let the whole invoice stall. Ask them to pay the undisputed amount by the due date, and put a date in writing for settling the disputed line. Log each message with its date next to the invoice, stop the sequence the moment the customer replies, and record what they promised. The tutorials on polite reminders for trades and three escalating late-payment letters go further on tone and timing, and staged payment requests cover longer jobs where the first invoice is a deposit.

Questions to put to your accountant before the template is final

Take the invoices above to your accountant as a draft and ask these seven things. Answers become fixed rules in your template, and your AI instruction can then state them as facts instead of leaving gaps.

1. At my turnover, must I be VAT-registered, and which rate applies to each type of job I do?
2. For each regular contractor customer, does the reverse charge apply, or has the customer told us in writing that it is an end user or intermediary supplier?
3. Which CIS rate applies to me, and do I qualify for gross payment status?
4. Should my invoice show an expected CIS deduction, or only the gross total?
5. How should I show materials I buy for a job, and what receipts must I keep?
6. What payment terms and late-payment wording should the footer carry for business customers and for householders?
7. How should numbering, cancelled invoices and credit notes work in my sequence?

Then run the same check before every invoice leaves: the number is new, the dates are right, labour plus materials equals the net total, the VAT line equals the rate times the net total (or the reverse-charge note is there and no VAT is in the total), the CIS line equals the rate times labour, the VAT number appears only if you are registered, and the terms match the footer. Seven checks take under two minutes and catch the errors described above.

Invoice questions tradesmen ask before sending

Does my invoice have to show the CIS deduction?

The contractor works out and takes the deduction when paying you, then gives you a payment and deduction statement within 14 days of the end of each tax month, so the statement is the record. Many subcontractors still show an expected deduction line on the invoice so the payment can be reconciled. Ask your accountant which you prefer, and keep labour and materials on separate lines either way.

Can I charge VAT before I am registered?

No. The official guidance says you must register for VAT before you start charging it, and a VAT number belongs on an invoice only once you hold one. Until then, leave the VAT lines and the number off, and ask your accountant when registration becomes compulsory at your turnover, since that threshold changes from time to time.

Can I add interest to an invoice for a homeowner?

The statutory interest and fixed sums are written for one business claiming from another, so they are not the tool for a private customer. For households, rely on the payment terms you gave before the job and a polite reminder sequence, and take advice before threatening formal action. Keep any late-fee wording reasonable and agreed in writing before the work starts.

Which AI tool should draft the wording?

Any mainstream chat assistant will do, such as ChatGPT, Claude or Copilot. The instruction matters more than the product: tell it to leave every figure and tax status as a placeholder, to invent no VAT number, and to flag what it assumed. Keep that instruction in a Project so each invoice starts the same way, and keep customer names and addresses out of the chat.

When should the first payment reminder go out?

A day after the due date is normal for a friendly nudge, with a firmer message a week later and a formal one about two weeks after that. If you agreed 14-day terms, the first reminder goes out on day 15. Quote the invoice number, amount and due date in every message so nobody has to work anything out.

Further reads

• Roofing Accounting Software: Deposits, Progress Invoices, Job Costing, AI — Deposits, progress invoices and job costing in accounting software.
• Painting Invoice Template: Deposits, Progress Billing and Chasing With AI — Deposits and progress billing in another trade.
• Hourly Rate for a Tradesman: Work Out Yours Without Guessing — Work out the rate those labour lines should carry.
• Can AI Check a VAT Return Before You File? Coding Error Checks — Check the VAT side before you file.
• AI Quote Generators for UK Tradesmen: Built-In or ChatGPT? — Quotes that match the invoices you send later.
• Tradie Invoice Template: Tax Invoice Wording and Reminders With AI — The same job with tax invoice wording and GST.
• AI Automation for Tradies: Quote Follow-Ups That Run Themselves — Automate the follow-up messages around quotes.
• AI Tools and AI Development: The Complete 2026 Guide — the AI hub, including every tutorial in the AI-for-business series.

Sources: official government guidance pages on invoice contents, VAT invoices, the VAT domestic reverse charge, the Construction Industry Scheme and late commercial payments, read in November 2026.