US Customs and Border Protection (CBP) told a court it cannot immediately refund about $166bn in tariffs deemed illegal by the Supreme Court. The taxes were imposed last year by Donald Trump under the International Emergency Economic Powers Act (IEEPA). The agency said its computer systems, administrative procedures and staffing do not enable it to comply at once with an order from Judge Richard Eaton requiring refunds to importers, with interest.

CBP said more than 330,000 importers filed over 53 million import entries tied to the tariffs. To handle the unprecedented volume, the agency plans to upgrade its Automated Commercial Environment (ACE) system to consolidate refunds by importer rather than process tens of millions of individual transactions. It said it expects to begin issuing refunds by the end of April.

The process follows a Supreme Court ruling on February 20 in Learning Resources v. Trump that struck down the tariffs because they were imposed without congressional authorization. The Trump administration could still appeal in federal court, potentially delaying the refunds sought by many importing companies.