The default mileage rate in QBO is the HMRC personal rate (45p/mile for first 10000 miles) but for company car users there are an array of different rates - all listed at https://www.gov.uk/guidance/advisory-fuel-rates - depending on engine size, and if the company car is an EV, or a diesel, etc.
A different QBO community post attracted the reply from a Intuit moderator that QBO uses HMRC rates only, and only allows the 45p/mile rate, and then didn't engage with a reply when pointed out that made no sense. After all, even this rate is invalid beyond 10000 miles. It is very unhelpful for QBO to impose the HMRC personal rate when a large number of UK users will be company car drivers who cannot claim that rate and have to use a different rate .. by law. Why does Intuit not allow different rates to be entered, but you could still allow the "default" rate as being 45p? Is this another example of the US company not understanding how UK taxation works?