There is quite a lot of local variation on how that is handled. In general, if the tank is owned by the seller and being transferred with the property, Pike's answer will prevail. Even if it is owned by the propane supplier but is a buried tank that would be a typical way of handling it (the buyer would probably rather continue with the same supplier than to have it dug up to be changed out). Free standing tanks owned by the supplier are sometimes handled that way but there are exceptions: 1) The supplier fills the tank and issues credit to the seller then, if the buyer opens an account with them, charges the buyer for the on site inventory (if not they pick up the tank). 2)The supplier picks up the tank, issues credit for the unused fuel to the seller, and the buyer makes their own arrangements for a supplier (sometimes even the same one).