Sales tax is a state-levied tax on all goods and services bought and sold within the state. For things that ship from different states, the sales tax of the sender is usually applied while the sales tax of the recipient is usually used for international orders. Each state sets its own sales tax rate and the total value of a purchase is then multiplied by the tax rate to calculate sales tax owed.

In the U.S. most items are eligible for sales tax. Everything from a stick of gum to a vehicle will incur sales tax. Sales tax is usually calculated automatically as a routine part of a transaction.

There are some products that are exempt from sales tax because they are seen as essential, though this can vary from state to state. In most states food items are considered too essential to be taxed, though that may only refer to certain, staple foods with sugary or unhealthy junk foods incurring sales tax or a separate excise tax. Another exempt category is prescription drugs, though over the counter medication may still be taxable.

Sales tax is typically collected by a business at the time of sale and the tax is then submitted to the authorities within a certain time period, sometimes annually, sometimes sooner. 

It is very difficult for an individual to fail to pay sales tax on a product they are buying. Most payment software will automatically calculate and apply sales tax and any long standing business will usually do the same as a matter of routine. However, it is possible for the business to fail to submit the collected sales tax to the proper authorities, usually the tax collector’s office. In the event of nonpayment of sales taxes, most often there will be a civil fee equal to the amount of sales tax owed in addition to any applicable fines and fees associated with delinquent filing. In the event that the business demonstrates a pattern of delinquent behavior, there may also be criminal penalties.