In most cases, this complexity is part of the underlying sales tax laws; but while a brick-and-mortar store has to deal with only the sales tax laws of its own location, remote sellers have to deal with the use tax laws of many jurisdictions—up to every US state and locality that assesses them, if the company has a presence or "nexus" in every state (as large "brick-and-mortar" sellers like Wal-Mart and Best Buy do).