STATISTICAL TREATMENT OF TAXES, CHARGES AND FEES
The System of National Accounts (SNA) defines a tax as unrequited while fees or charges render a service in return. However, the boundary between taxes and payments of fees and charges for services rendered is not always clear-cut. For example, if the service given in return does not match the payment provided (e.g. operation of motor vehicles) then the payment is treated as a tax rather than a fee.
It is worth noting the renewable energy certificates and the carbon pricing mechanism which are treated as a tax on production as there is no service being provided.
A charge imposed as a tax (e.g. payments for future cleaning of marine oil spillages) is treated as a charge rather than a tax because future service is being provided in case of emergency.