The point of sale (POS) or point of purchase (POP) is the time and place at which a retail transaction is completed. At the point of sale, the merchant calculates the amount owed by the customer, indicates that amount, may prepare an invoice for the customer, and indicates the options for the customer to make payment. It is also the point at which a customer makes a payment to the merchant in exchange for goods or after provision of a service. After receiving payment, the merchant may issue a receipt, as proof of transaction, which is usually printed but can also be dispensed with or sent electronically.

A receipt is a document acknowledging that a person has received money or property in payment following a sale or other transfer of goods or provision of a service. All receipts must have the date of purchase on them. If the recipient of the payment is legally required to collect sales tax or VAT from the customer, the amount would be added to the receipt, and the collection would be deemed to have been on behalf of the relevant tax authority. In many countries, a retailer is required to include the sales tax or VAT in the displayed price of goods sold, from which the tax amount would be calculated at the point of sale and remitted to the tax authorities in due course. Similarly, amounts may be deducted from amounts payable, as in the case of taxes withheld from wages. On the other hand, tips or other gratuities that are given by a customer, for example in a restaurant, would not form part of the payment amount or appear on the receipt.