In over 38 states, counties, cities, and special transit districts levy their own local option sales taxes on top of the statewide base rate. Consequently, the combined checkout tax rate can change simply by crossing a city or county line within states like California, Texas, or New York.

Never subtract the tax percentage directly from the receipt total. Instead, divide the gross total by (1 + Combined Tax Rate). For example, if your receipt total is $108.25 in an area with an 8.25% combined rate, the pre-tax subtotal is $108.25 / 1.0825 = $100.00.

In the vast majority of US states, unprepared grocery food and prescription medications are either completely exempt from sales tax or taxed at a reduced rate. Additionally, states like Pennsylvania, New Jersey, Minnesota, Massachusetts, and New York (under $110 per item) exempt everyday clothing and footwear.

Following the Supreme Court's South Dakota v. Wayfair ruling on economic nexus, most US states enforce destination-based sales tax sourcing for remote e-commerce sellers. That means online orders are taxed according to the combined state and local rate of the buyer's delivery address.

There are 5 states with no statewide sales tax (known by the acronym NOMAD): New Hampshire, Oregon, Montana, Alaska, and Delaware. (Note: Alaska permits local city-level sales taxes).

Because tax rates vary across thousands of local city jurisdictions and counties, retailers display pre-tax prices and calculate the applicable combined tax at checkout based on point-of-sale location.