NEW YORK (AP) — A refund system for businesses that paid tariffs which the U.S. Supreme Court ruled President Donald Trump imposed without the constitutional authority to do so launched Monday.

Importers and their brokers could begin claiming refunds through an online portal beginning at 8 a.m., according to U.S. Customs and Border Protection, the agency administering the system.

It’s the first step in a complicated process that also might eventually lead to refunds for consumers who were billed for some or all of the tariffs on products shipped to them from outside the United States.

Companies must submit declarations listing the goods on which they collectively put billions of dollars toward the import taxes the court struck down on Feb. 20. If CBP approves a claim, it will take 60-90 days for a refund to be issued, the agency said.

The government expects to process refunds in phases, however, focusing first on more recent tariff payments. Any number of technical factors and procedural issues also could delay an importer’s application, so any reimbursements businesses plan to make likely would trickle down to consumers slowly.

The co-owner of a clothing company based in Washington, D.C., said the system seemed buggy on Monday when she tried to create an account on the portal, which was required before companies could do anything else. A lawyer in Northern Virginia said his clients reported some system delays and lag time.

In a 6-3 decision, the Supreme Court found that Trump usurped Congress’ tax-setting role last April when he set new import tax rates on products from almost every other country, citing the U.S. trade deficit as a national emergency that warranted his invoking of a 1977 emergency powers law.

Although the court majority did not address refunds in its ruling, a judge at the U.S. Court of International Trade determined last month that companies subjected to IEEPA tariffs were entitled to money back.

Customs and Border Protection said in court filings that over 330,000 importers paid a total of about $166 billion on over 53 million shipments.

Not all of those orders qualify for the first phase of the refund system’s rollout, which is limited to cases in which tariffs were estimated but not finalized or within 80 days of a final accounting.

To receive refunds, importers have to register for the CPB’s electronic payment system. As of April 14, 56,497 importers had completed registration and were eligible for refunds totaling $127 billion, including interest, the agency said.

Meghann Supino, a partner at Ice Miller, said the law firm has advised clients to carefully list in their declarations all of the document numbers for forms that went to CBP to describe imported goods and their value.

“If there is an entry on that file that does not qualify, it may cause the entire entry to be rejected or that line item might be rejected by Customs,” she said.

Supino thinks the portal going live will require composure as well as diligence.

“Like any electronic online program that goes live with a lot of interest, I would expect that there might be some hiccups with the program on Monday,” she said. “So we continue to ask everyone to be patient, because we think that patience will pay off.”

Tariffs are paid by importers, and some companies pass on the tax costs to consumers via higher prices.

The system starting up Monday will refund tariffs directly to the businesses that paid them, which are not obligated to share the proceeds with customers. However, class-action lawsuits that aim to force companies, ranging from Costco to Ray-Ban maker Essilor Luxottica, to reimburse shoppers are winding their way through the U.S. legal system.