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 is scheduled to launch today.

Importers and their brokers will be able to 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 subsequently struck down. 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 could delay an importer’s application, so any reimbursements businesses plan to make to customers likely would trickled down slowly.

In a 6-3 decision, the Supreme Court on Feb. 20 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 Thursday, 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.