A sales tax is a tax, usually paid by the consumer at the point of purchase, itemized separately from the base price, for certain goods and services. The tax amount is usually calculated by applying a percentage rate to the taxable price of a sale.

A portion of the sale may be exempt from the calculation of tax, because sales tax laws usually contain a list of exemptions. Laws governing the tax may require it to be included in the price (tax-inclusive) or added to the price at the point of sale.

Most sales taxes are collected from the buyer by the seller, who remits the tax to a government agency. Sales taxes are commonly charged on sales of goods, but many sales taxes are also charged on sales of services. Advantages that a sales tax generally has over other forms of taxation are that it is difficult to avoid, and simple to calculate and collect.

A tax imposed on the sale of goods is depicted on the walls of ancient Egyptian tombs, which have been dated as far back as 2000 BC. These paintings describe the collection of tax for specific commodities, such as cooking oil.

A sale is the act of selling a product or service in return for money or other compensation. It is an act of completion of a commercial activity.

The seller' or salesperson – the provider of the goods or services – completes a sale in response to an acquisition or to an appropriation^{[disambiguation needed ][citation needed]} or to a request. There follows the passing of title (property or ownership) in the item, and the application and due settlement of a price, the obligation for which arises due to the seller's requirement to pass ownership. Ideally, a seller agrees upon a price at which he willingly parts with ownership of or any claim upon the item. The purchaser, though a party to the sale, does not execute the sale, only the seller does that. To be precise the sale completes prior to the payment and gives rise to the obligation of payment. If the seller completes the first two above stages (consent and passing ownership) of the sale prior to settlement of the price, the sale remains valid and gives rise to an obligation to pay.