As of 13 August 2026, AI can only partly forecast payroll costs for your UK small business.

What to actually do

1. Hand it to a person

   The route this page recommends

   A person who owns the outcome does this end to end, worth it when the failure is dear.

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 your payroll software, payroll spreadsheet and employment records, then export the latest employee pay, hours, pension and employer-cost data without including unnecessary personal information.
   2. List planned starters, leavers, pay changes, bonus payments, overtime, benefits and changes to working hours for the forecast period.
   3. Open the relevant GOV.UK payroll and pension guidance and copy the current assumptions you intend to use, including any rates or thresholds, into a separate note.
   4. Paste the payroll data, planned changes, employer policies, official assumptions and forecast timing into the prompt, then ask the AI to produce the base, lower-cost and higher-cost scenarios.
   5. Copy the resulting tables and formulas into Excel or Google Sheets, then compare each employee or category input against the payroll export and employment records.
   6. Recalculate the monthly totals in the spreadsheet and compare the tax, National Insurance and pension assumptions against the GOV.UK pages you opened.
   7. Ask your payroll administrator or accountant to check any missing rule, unusual worker arrangement or material difference before using the forecast for a hiring, pricing or cash-flow decision.

   Prompt

   Create a UK payroll cost forecast for [business name] covering [forecast period]. Use only the data and official assumptions I provide below, and do not invent missing figures. Separate each month into gross pay, employer National Insurance, employer pension contributions, bonuses, overtime, benefits, payroll fees and any other stated employer cost. Show each employee or worker category separately, then provide monthly totals and a total for the forecast period. Include three scenarios: base, lower-cost and higher-cost. Put every assumption in a separate assumptions table, including pay changes, hours, leavers, starters, bonuses, pension treatment and employer charges. If a UK payroll rule or rate is needed but I have not supplied it, mark it as missing and tell me which official GOV.UK source to check rather than estimating it. Show the formulas or calculation logic for every total so I can reproduce them in a spreadsheet. Flag missing, inconsistent or unusually changing inputs. Do not give tax or payroll advice, do not prepare a filing, and label the result as a planning forecast. Return a clear table suitable for copying into Excel or Google Sheets, followed by a short list of checks I must complete before relying on it.
   
   Payroll data:
   [paste payroll export, employee pay details or category totals]
   
   Planned changes:
   [paste known starters, leavers, pay rises, hours changes, bonuses and overtime]
   
   Employer policies and costs:
   [paste pension, benefits, payroll fee and other employer-cost details]
   
   Official UK assumptions:
   [paste the GOV.UK guidance, rates and thresholds you want used]
   
   Forecast timing:
   [paste the start date, end date and payment frequency]
   
   Current budget or comparison figures:
   [paste any figures to compare against]

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