As of 13 August 2026, AI can only partly calculate UK PAYE tax.

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 employee's current payslip, starter declaration or P45, tax-code notice and payroll record, and gather the gross pay, taxable pay year to date, income tax year to date, tax code, tax basis and taxable benefits.
   2. Check GOV.UK or HMRC for the relevant tax year, pay frequency and PAYE guidance, and save the source links alongside the payroll record.
   3. Remove unnecessary personal identifiers from the figures, then paste the gathered inputs and the prompt into ChatGPT, Claude or Gemini.
   4. Ask the model to calculate PAYE income tax only and to stop if a required input or current HMRC rule cannot be confirmed.
   5. Compare the model's assumptions, tax basis and arithmetic with the payslip, HMRC guidance and the employer's payroll software output.
   6. Send any difference, unusual tax code, starter-leaver issue or taxable-benefit treatment to the payroll manager or an accountant before payroll is finalised.

   Prompt

   Calculate the UK PAYE income tax deduction for this pay period using only the information below. Treat the result as a checking calculation, not as a payroll filing or a definitive tax answer.
   
   Use the relevant HMRC rules and rates for the tax year and pay frequency stated below. If you cannot confirm a current rule from an official GOV.UK or HMRC source, say so and do not guess. Show each step, identify whether the calculation is cumulative or non-cumulative, and distinguish taxable pay from non-taxable pay. Do not calculate National Insurance unless I ask for it separately.
   
   Tax year: [tax year]
   Pay frequency: [weekly, fortnightly, four-weekly or monthly]
   Gross pay for this period: £[amount]
   Taxable pay year to date: £[amount]
   Income tax paid year to date: £[amount]
   Tax code exactly as shown: [tax code]
   Tax basis if shown: [cumulative or Week 1/Month 1]
   Previous pay and tax details available on the starter declaration or P45: [details or not available]
   Taxable benefits or adjustments: [details or none]
   Other payroll notes: [details or none]
   
   Return:
   1. The estimated PAYE income tax deduction for this period.
   2. The estimated net pay before National Insurance and other deductions, only if the supplied information supports it.
   3. A table of the inputs used.
   4. Every assumption and missing input that could change the result.
   5. A plain explanation of how to verify the result against the employee's payslip and the employer's payroll software.
   6. Links to the GOV.UK or HMRC sources used.
   
   Do not invent figures, tax codes, allowances, benefits or HMRC rules. If the inputs are insufficient, stop and list exactly what is missing instead of producing a confident number.

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