According to CyclingUK.org, "Employees who use their own cycle for work (i.e. for cycling on business, not to and from work) are entitled to 20p per mile, tax-free. (N.B. there are different arrangements for self-employed people who use their cycles for business purposes." https://www.cyclinguk.org/article/campaigns-guide/tax-incentives#:~:text=Cycle%20mileage,their%20cycles%20for%20business%20purposes.

We need this for mileage in the U.K.