What does the difference invoice mean?

Taxpayers who collect the difference shall deduct the prescribed project price paid to other taxpayers from the total price and out-of-price expenses obtained to calculate tax payment. For enterprises that collect the difference, the invoice issued is the difference invoice. For example, taxpayers who provide property management services charge tap water fees to clients, and the balance after deducting the tap water fees paid by them is sales. According to the simple taxation method, VAT is calculated and paid at the rate of 3%.