As of 13 August 2026, AI can only partly add the correct VAT to an invoice.

What to actually do

1. Hand it to a person

   The route this page recommends

   Someone with a licence or accountable authority has to sign this before it counts.

2. Use a tool built for this

   Second choice

3. Do it yourself

   The distant third

   A chat interface, chat-fluent skill, and roughly 30 minutes until you can act on the result.

   How to actually do it

   1. Open the draft invoice and record the supplier's VAT registration status, customer location and VAT status, goods or services, tax point and net amount for every line.
   2. Open the relevant GOV.UK or HMRC VAT guidance and check whether the supply could be standard-rated, reduced-rated, zero-rated, exempt, outside the scope or subject to reverse charge.
   3. Paste the gathered facts into the prompt, keeping each line item and net amount separate, and ask the chatbot to stop if the treatment or rate is not established.
   4. Compare the chatbot's proposed VAT treatment, rate and invoice wording against the current GOV.UK or HMRC guidance for that supply.
   5. Recalculate each VAT amount yourself using the stated net amount and rate, then check the subtotal, total VAT and grand total to two decimal places.
   6. Enter the checked net amounts, VAT rates, VAT amounts and any required wording into the invoice, and ask a UK VAT accountant to confirm unusual or material transactions before sending.

   Prompt

   Calculate the VAT for this UK invoice, but do not guess the VAT treatment or rate. First list the facts that are missing, including the supplier's VAT registration status, the goods or services supplied, the tax point, the customer's country and VAT status, and whether any special rule may apply such as zero-rating, exemption, reduced rating, reverse charge or place-of-supply rules. If the treatment is not established by the information below, stop and say what must be confirmed from current GOV.UK or HMRC guidance or with a UK VAT accountant.
   
   If the treatment and rate are established, show:
   1. Net amount for each line
   2. VAT rate for each line
   3. VAT amount for each line, rounded to two decimal places
   4. Invoice subtotal, total VAT and grand total
   5. Any legally important invoice wording that follows from the treatment
   
   Show the arithmetic so I can check it. Do not invent facts, rates, exemptions, customer details or invoice wording. Separate confirmed calculations from assumptions. Use pounds sterling.
   
   Invoice and transaction details:
   Supplier VAT status: [insert]
   Supplier location: [insert]
   Customer location and VAT status: [insert]
   Goods or services: [insert]
   Tax point: [insert]
   Line items and net amounts: [insert]
   Possible special VAT rule: [insert or 'unknown']

   Open it prefilled in ChatGPT or Claude, or copy it into Gemini, which takes no prefill link.