Kim Batten, a physical therapist from Oakland, bought a trench coat this year from a Dutch retailer for $456, a price that was a little above her budget.

But after the coat was shipped, UPS told Batten in an email that she would have to pay over $250 in customs duties to receive it. With shipping, the whole transaction came to well over $700.

“It ended up being the second most expensive article of clothing I’ve ever bought, other than my wedding gown,” she said.

For decades, no customs duties were imposed on items like Batten’s coat. But this year, President Donald Trump closed a loophole that had allowed goods worth $800 or less to enter the United States tariff free. The loophole, known as the de minimis exemption, ended for items from China in May and for the rest of the world in August. Shoppers must now pay duties for the first time, often in amounts far higher than they expected.

“I’m definitely more leery about where I’m shopping now,” Batten, 35, said.

Democrats and Republicans favored ending the exemption on low-value goods. They said it helped large sellers, particularly those from China, evade tariffs, and made it easier to smuggle fentanyl into the country. Other countries are now planning to end or tighten de minimis exemptions.

Still, the abruptness with which the United States closed the loophole caused major disruptions for sellers of all sizes, as well as for express carriers like FedEx and UPS, postal networks and American shoppers.

“It’s been a bit of a whiplash for sure,” said Clint Reid, CEO of Zonos, which provides software that enables sellers to calculate and pay tariffs.

Before the policy changes, an average of around 4 million de minimis packages entered the United States a day. The number of packages worth $800 or less coming into the country is now much lower.

Since Aug. 29, when the loophole closed for all countries, Customs and Border Protection has cleared over 70 million shipments that would previously have qualified for the exemption, according to a spokesperson for the agency, implying a daily average inflow of over 800,000 packages. The spokesperson said the agency had “assessed over $400 million in duties” on the packages.

“Volumes of packages coming into the U.S. continue to increase as exporters adjust” to the new policies, the spokesperson added.

Foreign sellers are responding to the new regime in different ways.

Instead of sending items individually from overseas, some foreign retailers have begun shipping their goods to the United States in bulk, paying tariffs at the border, and distributing them to consumers from American warehouses. And some foreign sellers who continue to sell directly to shoppers in the United States have also decided to pay tariffs themselves.

In both cases, the sellers may mark up prices to cover all or some of the duty, but American recipients would not have to make a customs payment to get the package.

But some sellers choose not to pay the tariffs themselves, and ask their customers to do so. That’s why shoppers need to scrutinize the checkout process and look at the fine print on sellers’ websites.

Some overseas retailers calculate the tariff amount at checkout, giving buyers an opportunity to decide whether they want to complete the purchase. Ssense, an online boutique based in Montreal, discloses tariffs amounts to customers in this way.

The big surprises occur when sellers don’t collect tariffs from buyers at the time of purchase — and don’t say how much consumers might have to pay later.

Some sellers give clear warnings that duties might have to be paid but don’t state the amount.

This, too, can catch buyers unaware.

Claudia Scholtz, 78, an avid weaver from Portland, Oregon, paid Jane Stafford Textiles, a Canadian seller, $158.36 for leg extensions, pieces of wood that raise a loom. Jane Stafford clearly warns American customers at checkout that they will likely have to pay tariffs to UPS later.

UPS notified Scholtz that she would have to pay $333.50 in duty to receive the parts.