A Billing Specialist oversees the tasks of sending new invoices to clients and ensuring all outstanding invoices are paid in full and on time. They are client-focused and assist them with any issues with invoices. The duties and responsibilities of a Billing Specialist include sending invoices and account updates to clients, receiving, sorting, and tracking incoming payments, addressing and resolving client questions and issues relating to invoices, and providing regular, accurate reports of billing data. A billing systems operator reviews purchase orders and sale records to determine how much each customer is to pay. This may entail preparing and mailing invoices to customers.