Invoice books record your sales and purchases. They can be used to keep track of the cash flow of your enterprise or business. Aside from its basic functions listed above, invoice books can be used for other roles in different parts of your business. They can also be used...   Invoice books record your sales and purchases. They can be used to keep track of the cash flow of your enterprise or business. Aside from its basic functions listed above, invoice books can be used for other roles in different parts of your business. They can also be used...