WASHINGTON — The Supreme Court is hearing a case this week that could affect how much customers pay for online purchases.

At issue is a rule saying that businesses don't have to collect state sales taxes when those businesses ship to a state where they don't have an office, warehouse or other physical presence.

Large retailers with brick-and-mortar stores have to collect sales taxes nationwide, but smaller online sellers can often avoid doing so.

Large retailers say the rule puts them at a competitive disadvantage. States say they're losing out in billions of dollars in tax revenue.

But small businesses that sell online say the complexity and expense of collecting taxes nationwide could drive them out of business.