What is the purpose of an invoice?

What is a sales receipt? Are sales receipts legally required? Can sales receipts be used for tax purposes? How long should I retain sales receipts? Can I issue digital sales receipts instead of paper ones? What is the main difference between an invoice and a receipt? When should I issue an invoice? What information should be included in an invoice? Can I issue an invoice after receiving payment? What is an invoice? Why is invoice accuracy important? What information should be included in an invoice? (1) Are there legal requirements for invoices? How to ensure timely payment for invoices? Why is it important to efficiently pay an invoice? What are common payment methods for invoices? How can I ensure accuracy when making payments? Can I schedule recurring payments for regular invoices? What is the main difference between a purchase order and an invoice? Are purchase orders legally binding? When should a purchase order be used? What is a purchase order process? Why is optimising the purchase order process important? What are some best practices for optimising the purchase order process? How can optimising the purchase order process help outrank competitors?