The "de minimis" trade loophole that allowed cheap packages to come to the U.S. duty-free is closing. Ecommerce customers are already feeling the sting.

A duty-free loophole for low-value packages is about to be closed by President Donald Trump, pushing up prices for US customers of firms like Shein and Temu.The Chinese online retail giants relied on the so-called "de minimis" exemption to sell and ship low-value items directly to the US without having to pay duties or import taxes.

The Chinese web retailers on Friday hiked prices to offset a 120% tariff that their goods will be subject to with the May 2 end of the de minimis exemption, which has allowed retailers to import goods worth less than $800 into the US without paying tariffs.