Creating a receipt nominal code is used for posting a vehicle receipt to a certain nominal code.
This is set up by going in Vehicles> Vehicle Parameters Maintenance> Receipt Nominal Code> Click the 'Add' button and a pop up window will appear, enter a description (this text will appear as a drop down payment method when posting a receipt against a vehicle), then enter the nominal code and hit close, then click the close on the main screen to save.
This will make it appear as an available payment method within the Debtors tab > Post Receipt.