Costco Wholesale is facing a nationwide class action in the US seeking refunds for customers who allegedly paid higher prices due to import tariffs later ruled unlawful.

The lawsuit was filed by a Costco shopper in a federal court in Illinois.

It seeks a declaration requiring the retailer to return to customers any refunds it receives for tariffs paid under the International Emergency Economic Powers Act (IEEPA).

The complaint comes after a 20 February ruling by the US Supreme Court that US President Donald Trump exceeded his authority by invoking emergency powers legislation to impose sweeping tariffs last year.

The ruling has prompted extensive litigation before the US Court of International Trade, where more than 2,000 companies, including Costco, are pursuing reimbursement for duties paid under the tariffs.

According to the complaint, Costco passed the cost of IEEPA tariffs on to customers by increasing prices and may receive refunds from the government if the ongoing trade cases succeed.

The filing notes retaining those refunds without compensating customers would result in “windfall profits generated by the unlawful tariffs imposed by the Trump Administration under the International Emergency Economic Powers Act”.

It notes that under US trade law, only importers of record are allowed to recover tariff refunds from the government.

However, the financial burden of those tariffs was largely passed on to consumers through higher retail prices.

The plaintiff alleges that Costco passed tariff-related costs on to customers while also potentially receiving government refunds.

The lawsuit asks the court to order Costco to reimburse the plaintiff and proposed class members for all IEEPA-related duties that were allegedly passed on through higher prices.

It also seeks interest, plus reasonable attorneys’ fees and costs.

The complaint also references remarks made by Costco CEO Ron Vachris on 5 March 2026, stating that any tariff refunds the company receives would be used to provide “lower prices and better values” to Costco members generally.

However, the lawsuit argues that the statement does not amount to a commitment to compensate customers who paid higher prices during the period when the tariffs were in effect.