Tariffs are on. Tariffs are off. Tariffs are delayed.

Importers, shippers and American ports are struggling to stay on top of the ups and downs of the U.S.-China trade war. Some businesses, but not all, received temporary relief from the latest round of tariffs from the Trump administration this week.

Most of the import taxes that were supposed to kick in on Sept. 1 are now delayed until December, but many businesses had already made plans to adapt to the latest salvo in the trade war.

“As companies put their mitigation plans in place, it costs money,” said Jonathan Gold, vice president of supply chain and customs policy at the National Retail Federation. “Whether it’s … trying to find alternate vendors or speeding up your shipments — I mean, all this comes at a cost.”

The short notice for possible tariffs sends businesses scrambling to get their products to the United States before the new import taxes kick in. Vincent Iacopella at Freight Forwarders and customs broker Alba Wheels Up has been through this before. He pointed to the rush back in December to beat a Jan. 1 tariff deadline.

“It had a profound effect on capacity, had a profound effect on port congestion,” said Iacopella, who is also the president of the Pacific Coast Council of Customs Brokers and Freight Forwarders Association. “We had 31 ocean vessels call the port complex of L.A. Long Beach that weren’t scheduled to call.”

He said that rush caused delays, equipment breakdowns and, of course, higher costs for businesses.