https://www.gov.uk/government/publications/paye-car-and-car-fuel-benefit-p11d-ws2
PAYE: car and car fuel benefit (P11D WS2 and WS2b) - GOV.UK
Use form P11D WS2 and P11D WS2b if you're an employer and need to work out the cash equivalent of providing car and fuel benefit to an employee.
car and fuelpayebenefitp11dws2