U.S. citizens only pay VAT when in Europe or another country with a value-added tax. The U.S. does not operate a VAT system. Instead, U.S. sales tax is administered by individual states, not the federal government. It applies sales tax at the final point of sale, which is collected by the seller and remitted to the appropriate state or local authority.
Sales tax rates vary across thousands of jurisdictions, including states, counties, and cities. Because of this complexity, sales tax is usually added at checkout rather than included in the listed price.
You don’t — the U.S. doesn’t have VAT. Sales tax is calculated instead, based on the rules and rates in effect at the buyer’s location, which can differ from one jurisdiction to another.