Sales tax is a consumption tax charged at the point of sale on goods and services. In the United States, sales tax rates are set by state and local governments and vary significantly by location. Some states have no sales tax at all, while others combine state and local rates that can exceed 10%.

To add tax: Total = Price x (1 + Tax Rate / 100). To reverse-calculate the pre-tax price from a tax-inclusive total: Pre-Tax Price = Total / (1 + Tax Rate / 100). The tax amount in either case is the difference between the total and the pre-tax price.

For example, an item priced at $89.99 with an 8.25% sales tax incurs $7.42 in tax for a total of $97.41. Conversely, if you paid $97.42 including tax and the rate is 8.25%, the pre-tax price was approximately $90.00 and the tax was $7.42. This reverse calculation is useful for expense reporting and accounting when receipts show only the total amount.