Add a new Item/Service
On any Invoice. Memorized Invoice or Credit memo Item List.
Click Add New Row
Under the Column Item/Service, If the Item you need it not there. Simply Type the name of the Item you would like to Create.
For this Example I am going to Call this Item "FoxTrot Prepayment" You will see a popup below the item that says to hit enter to add the item
Hit Enter and a Modal will appear, Typically most users for services click always one each. and then select the Account you wish to link to the Item/Service