What is the function of an invoice?

As per the Cambridge dictionary the definition of an Invoice is "a list of things provided or work done together with their cost, for payment at a later time:"

However the main and most important function of an invoice is to serve as an evidence or a supporting document for the occurrence of a particular transaction.

In addition the following functions are evident in an Invoice.

1.Provides information regarding price and quantity of a transaction

2. Provides information regarding the details of supplier such as name, address, business registration number, tax identification number of supplier.

3. Provides details regarding the customer to whom it is invoiced.

4. Acts as a legal document or a document to support encase of an issue regarding a particular transaction etc,.