Generally speaking, when you book a service provider for any type of experience whatsoever, you should be told what the final and fixed price is going to be. However, there are certain companies that would operate rather unethically in that regard. What this basically entails is that they might include some secret charges and hidden fees into the bill that you would need to settle, which would obviously destroy the budgetary guidelines that you had been hoping to work with. Suffice it to say that learning about these hidden fees can go a long way towards helping you to avoid them to the best of your abilities.
Firstly, some charter bus rentals that prioritize profit above all else might withhold some crucial information that would reveal how fuel is not included in the rental amount. This is mostly because of the fact that they want the rental fees to go entirely towards lining their pockets, and that is certainly going to make the price a bit too much for you to be able to afford. At the end of the day, if the service provider is charging for fuel separately, it is their responsibility to be transparent about it.
Now that we have gotten all of that out of the way, it is important to mention that reputable and trustworthy charger bus providers will never even dare to try to charge you a secret fee of any sort. They know that doing so will betray the trust that their customers have placed in them, and they would steer clear of doing anything so underhanded. Always try to find a company that is upfront about all of their charges and you should be good to go.