Authorization and Voucher for Expert and Other Services is a process to ensure that an organization is able to prove that an expert or other service provider was engaged and paid to provide goods or services. Authorization and Voucher for Expert and Other Services provides an authorization number or voucher that ensures that the organization has taken the necessary steps to protect itself from fraud and potential legal issues. The two main types of Authorization and Voucher for Expert and Other Services are Purchase Order (PO) and Purchase Requisition (PR). A Purchase Order is an official document issued by the organization that authorizes the purchase of goods or services. A Purchase Requisition is a formal request from the organization to obtain goods or services from a third-party vendor. Both types of Authorization and Voucher for Expert and Other Services require an authorization number or voucher to be issued before payment is made. Another type of Authorization and Voucher for Expert and Other Services is the Pro Forma Invoice. A Pro Forma Invoice is a document that provides an estimate of the cost of goods or services that have not yet been ordered. This type of Authorization and Voucher for Expert and Other Services requires an authorization number or voucher to be issued before payment is made. The final type of Authorization and Voucher for Expert and Other Services is the Payment Request. A Payment Request is a formal request from the organization to a third-party vendor for payment of goods or services provided. This type of Authorization and Voucher for Expert and Other Services requires an authorization number or voucher to be issued before payment is made.