Thankyou Fran for a speedy reply.
I find myself placed in the above situation as an employee for a large rental company. I do not agree with it in any form. I believe the tank should be refilled after every rental and the customer billed as such.
As the vehicles are not correctly checked in after rent the fuel gauge my show full but the tank can be short of upto 80 litres of fuel.
After a heated talk with a manager about this issue ive been told to go off the gauge and ignore the tank even though I have check it. It can not be right to do this and I find myself at the risk of being disciplined.
Thank you Fran for your help, the company is international including US, but you are right that it is better dealt with in the UK. The disciplinary is not the issue here, I just wanted to confirm what is happening is wrong. I will not disclose any info gained here.