An invoice has a bit of flexibility. Certain firms’ will give incentive for early payments or give penalties for late payments. Most of the time, if a customer decides to pay early, they could receive a discount on the costs. Invoice data can be altered by issuing debit or credit notes.

A business will issue an invoice after the completion of a project, it includes the supply of services or sale of goods. 

An invoice is a fixed document, because it is prepared when the project is completed and takes into account all project data.

An invoice includes and describes the details of the products or services provided to the customer, the desired mode of payment, and the total amount owed.

Once the estimate has been delivered, the two parties can then discuss it. Then, a revised estimate is made to compensate any specific changes based on negotiations. This helps gain an idea of the exact cost that needs to be paid from the clients to the business. 

Before a business engages in contract documents, they will offer the customer an estimate so that they can gather an approximation of how much they may owe.

An estimate offers an approximate number of the total cost to be paid. It also estimates the expected turnaround time.

An estimate is a detailed document that you send to a client when you want to explain the approximate (estimated) amount you predict you will need to charge for the goods or services of your project. A potential client can then decide if they want to accept or reject the estimate.