A loophole that has allowed American shoppers to buy lots of cheap goods from mainland China and Hong Kong without paying tariffs and filling customs forms is closing on Friday.

Prices have already gone up.

Orders for many imported goods from retailers like Shein and Temu could dwindle as consumers balk at the higher prices and new inconveniences. But, like much of President Trump’s trade war, the administration’s policy on the loophole has gone through changes. The president had ordered that the loophole be closed in February, but then reinstated it within a few days. Logistics experts said the short closure caused a pileup of packages at the borders.

What exactly is going away?

Since 2016, items worth $800 or less could be imported into the United States without the recipient’s paying tariffs or even filing the paperwork typically associated with purchases of foreign goods. The loophole is known as the de minimis exemption. Mr. Trump is eliminating the exemption only for goods from mainland China, the largest source of de minimis shipments, and Hong Kong.

A report for Congress this year said Customs and Border Protection processed over one billion de minimis packages a year. The average value of the shipments in 2023 was $54.

Shipments worth under $800 have been exempt because Congress believed the expense and inconvenience of processing them would not justify the customs revenue. Mr. Trump is ending the exemption, in part, to try to prevent the flow of fentanyl and fentanyl’s precursor substances into the United States via de minimis shipments.

De minimis shipments ballooned after Mr. Trump imposed tariffs on China during his first administration, suggesting that people and businesses were turning to smaller packages to avoid tariffs.

How is this hitting shoppers?

Since tariffs on Chinese goods are punishingly high, de minimis goods are already starting to cost a lot more.

That’s evident to shoppers on the Chinese e-commerce site Temu. The company recently began detailing the cost that tariffs would add to their purchases.

For example, a cart of 10 items from Temu, including a 50 pack of heavy-duty hangers for $70.50, a men’s green linen shirt for $19.38 and a fluffy pink dog bed for $24.05, came out to $275.03, including international freight charges, and $10.20 in sales tax. But at checkout, the website tacked on $343.26 in import charges, bringing the total to $628.49. (Temu does give shoppers the option of buying goods marked as coming from local warehouses that do not incur import charges.)

At Temu’s rival Shein, a cart of 10 similar items came out to $244.03. Though it didn’t detail additional import charges on the goods, Shein’s website told shoppers: “Tariffs are included in the price you pay. You will never have to pay extra at delivery.”

Still, shoppers said they’d seen prices for some items on Shein’s website rise over the weekend. Even though the tariff exemption isn’t expected to end until Friday, the charges are appearing already because orders placed now won’t cross the border until after.

Lindsay Olive of Atlanta, who shops regularly on Shein, put a number of summer dresses in her cart last week, including a blue one for $10.88 and a floral one for $11.29. When she went to check out this weekend, the price for the blue dress had increased to $13.88 and the floral had jumped to $15.43, according to screen shots she shared.

“I knew things were going to start going up in price, and I wanted to get some summer dresses before that happened,” Ms. Olive, 39, said. She expects prices will climb further.

Amazon said on Tuesday that it had considered detailing import charges on the part of its site — called Amazon Haul — that competes with Temu, but decided not to.

“Teams discuss ideas all the time,” the spokesman, Ty Rogers, said in a statement. He said it was never under consideration for the main Amazon site, adding: “This was never approved and is not going to happen.”

The import charges can differ depending on how the goods are shipped. If they come on an express carrier like DHL or FedEx, the goods will be subject to tariffs as high as 145 percent, or $14.50 on a $10 T-shirt.

Shipments coming in through the Postal Service will face a tariff equivalent to 120 percent of the value of the goods, starting Friday, or a fee of $100 per package. The fee increases to $200 in June.

What about the paperwork?

One of the conveniences of a de minimis shipment is that the recipient does not have to provide a Social Security number to get the goods, as is the case with other types of imports.

Instead, de minimis goods require only a name and an address.

As of Friday, de minimis shipments from China will be classified as “informal entry” imports. Informal entry goods, which can be worth up to $2,500, do not require a recipient’s Social Security number, Customs and Border Protection said in a statement. Still, the agency said in January that carriers often require Social Security numbers because having them speeds up clearance through customs.

FedEx said that, in accordance with Customs and Border Protection requirements, it would not require Social Security numbers on shipments from China that lose their de minimis exemption on Friday. DHL said it would not require Social Security numbers on informal entry shipments. UPS declined to say whether it would require Social Security numbers, but the company added that it had the expertise to help its customers “navigate global trade and follows all applicable laws and regulations.”

A representative for the Postal Service said it would “not have a role in duty collection for items of de minimis value postal shipments.” Instead, the tariffs would have to be collected by the carrier bringing the goods into the United States.

Will there be delays?

Collecting tariffs and checking a much larger number of packages could become a challenge for carriers and Customs and Border Protection. But it is not clear whether those actions would delay packages more than a day or two or much longer.

The customs agency said in a statement that although it had “a huge task on its hand,” it was “uniquely positioned to implement and enforce the president’s tariffs.”

Ana Swanson and Madeleine Ngo contributed reporting.

UPS said on Tuesday that it would cut 20,000 jobs this year as part of a long-term plan to reduce costs and bolster profit.

The cuts come as President Trump’s tariffs are prompting some UPS customers to ship fewer goods. The company said “macroeconomic uncertainty” prevented it from updating its forecasts for revenue and profits for 2025.

UPS already cut 12,000 jobs last year. It now has some 490,000 employees, many of whom are members of the Teamsters union. In its latest cuts, the company said it would shed “operational” employees, or those who sort or deliver packages. UPS also said it would close 73 buildings by the end of June.

UPS has been trying to improve its profit margins, partly by reducing costs and shedding parts of its business that don’t make money. The company has said many of the deliveries it does for Amazon, its largest customer, are not profitable. It plans to slash in half the volume of packages it delivers for Amazon by the middle of next year.

In all, UPS plans to reduce costs by $3.5 billion this year. Most of that sum is expected to come from the job cuts and building closures, but the company also anticipates savings from reducing the number of hours its employees work. UPS has 412,000 hourly employees, about half of whom are part time.

In 2023, the Teamsters and UPS agreed to a five-year labor contract that included wages that were significantly higher than at nonunion delivery companies. Commenting on the job cuts Tuesday, the Teamsters’ general president, Sean M. O’Brien, said the contract requires UPS to create 30,000 Teamster jobs.

“If UPS wants to continue to downsize corporate management, the Teamsters won’t stand in its way,” Mr. O’Brien said in a news release. “But if the company intends to violate our contract or makes any attempt to go after hard-fought, good-paying Teamsters jobs, UPS will be in for a hell of a fight.”

A UPS spokesman said the company would adhere to the contract.

On a call with investors Tuesday, UPS’s chief executive, Carol Tomé, said Mr. Trump’s trade policies were particularly debilitating for small and midsize businesses that buy goods from China. The president has raised tariffs by as much as 145 percent on many goods imported from that country.

Ms. Tomé said smaller companies, which didn’t have the financial wherewithal to stock up before the tariffs took effect, are now saying, “Wow, how are we going to handle this cost increase that’s coming our way?”

Ms. Tomé said deliveries from China to the United States were UPS’s most profitable trade lane and responsible for 11 percent of the company’s international revenue. The company said it expected its China-to-United States business to decline.

But Ms. Tomé also said UPS would be able to respond to any shift in supply chains caused by the tariffs. In Mr. Trump’s first term, Chinese exports to the United States declined, but trade grew between China and rest of the world, she said, noting that UPS’s international business also grew in that period.

“We can move where supply chains move,” Ms. Tomé said.

European carmakers, including Mercedes-Benz, Stellantis and Volkswagen, said Wednesday that the chaos and upheaval caused by the tariffs introduced by President Trump had left them struggling to assess the impact and unable to plan for the future.

After years of sluggish demand and high inflation, Europe’s carmakers headed into 2025 with a raft of new battery-powered models and high hopes that they would lure back customers.

Instead, they are faced with global uncertainty surrounding supply chains and customer demand, set off by Mr. Trump’s decision to impose 25 percent tariffs on all cars, steel and aluminum coming into the United States.

On Wednesday, Mercedes-Benz suspended its financial forecasts for 2025, as did Stellantis, which includes Fiat, Peugeot and Opel among its brands in Europe, and Chrysler, Dodge and Jeep in the United States.

“The current volatility with regard to tariff policies, mitigation measures and resulting potential direct and indirect effects in particular on customer behavior and demand is too high to reliably assess the business development for the remainder of the year,” Mercedes-Benz said in a statement on Wednesday.

Stellantis cited “the evolution of customs tariffs, as well as the difficulty in predicting their potential impacts on the market and the competitive landscape” for its decision.

Volkswagen Group, the largest automaker in Europe, decided not to scrap its outlook for 2025, but instead scaled back its profit expectations to the lower end of its forecast, to between 5 and 6 percent. The company, which owns Audi, Porsche and the Volkswagen brand, cautioned that the initial calculations had been made before the tariffs were introduced in early April.

All three companies have factories in the United States. Mr. Trump on Tuesday announced changes to the tariffs in what he called “a little flexibility” toward automakers that produce cars in the United States and are concerned about the damage the import taxes will do to their business.

Under the latest version, carmakers that pay a 25 percent tariff on auto imports are not subject to other levies, like, for example, on steel and aluminum, or on certain imports from Canada and Mexico. However, the rules do not appear to protect automakers from tariffs on steel and aluminum that their suppliers pay and may pass on.

The leading group representing German automakers welcomed the move by Mr. Trump, but called it “a small step” that only slightly eases the burden caused by the tariffs.

German carmakers operating in the United States have been caught off guard by the imposition of import taxes on parts and vehicles coming in from Canada and Mexico, where many set up operations after Mr. Trump reworked the free-trade agreement with those countries during his first term in office.

“Companies urgently need more clarity in order to be able to assess the exact impact and implement the measures with legal certainty,” said Hildegard Müller, president of the German Association of the Automotive Industry.

Porsche has been among the German brands hardest hit by the tariffs. It relies on the U.S. market for 40 percent of its sales, but manufactures its sports cars exclusively in Germany, leaving it heavily exposed to the duties.

The sports car maker’s dismal performance in the first three months of the year dragged down its parent company, Volkswagen Group, which said Wednesday that its earnings dropped more than 40 percent in the first quarter.

Even before Mr. Trump introduced tariffs, Volkswagen’s key brands were struggling against high costs and overcapacity at its plants in Germany, as well as increased pressure from Chinese competitors that are flooding the European market despite an increase in import taxes passed by the European Union last year.

Volkswagen makes cars including the electric ID.4, at a factory in Chattanooga, Tenn., and is building a factory in South Carolina to produce off-road vehicles under the Scout brand. Audi produces cars in Europe and Mexico, as well as Europe, but not in the United States. Oliver Blume, Volkswagen’s chief executive, has said that the company is considering shifting manufacturing of another one of its models to Chattanooga to avoid tariffs.

German media has reported that Mr. Blume and his counterparts at Mercedes-Benz and BMW met with Mr. Trump in an effort to work out a deal. German automakers and their suppliers employ some 138,000 people in the United States, according to the German industry trade group.

The tariffs are causing other European carmakers to rethink their strategy in the United States. The British automaker Aston Martin said Wednesday that it was holding back on imports to the United States because of the tariffs. Instead, the company plans to use up existing inventory that has already been shipped, the company’s chief executive said in a statement. Jaguar Land Rover has also said that it is pausing shipments to the United States.

One hundred days of President Trump. Seventy days of whipsaw trading in financial markets. Thirty three days of losses. More than $6.5 trillion wiped from the value of public companies.

For financial markets, the 9 percent drop in the S&P 500 is on track for the worst start to a presidential term since Gerald R. Ford took over from Richard M. Nixon in August 1974 after the Watergate scandal. The slump is worse even than when the tech bubble burst at the turn of the century, and George W. Bush inherited a market already in free fall.

In contrast, Mr. Trump inherited an economy on solid footing and a stock market rising from one record high to another.

That swiftly changed when Mr. Trump unveiled his marquee suite of tariffs on April 2 — not the first new import taxes announced by his administration, but by far the most sweeping. Volatility erupted. Wall Street frantically began to grapple with the economic consequences of the new government’s policies.

The S&P 500 tumbled more than 10 percent in two days, a drop comparable to some of the worst days of the pandemic-induced sell-off in March 2020 and, before that, the financial crisis in 2008.

Stocks have since stabilized, but the shock waves from the chaotic tariff rollout continue to send tremors through the global financial system.

Some investors have questioned the United States’ role at the heart of that financial system and the safety of the nation’s assets during periods of market turmoil, threatening the long-held market order.

There remain some optimists who note that the market turmoil did seem to eventually prompt Mr. Trump to back down on his steepest tariffs. But for many investors, even hopes of trade deals, tax cuts and deregulation — a return to the more pro-business policies on the president’s agenda — remain marred by the sheer uncertainty over what else could happen next.

“It’s a very unstable situation,” said Michael Purves, chief investment officer at Tallbacken Capital.

Promises of Prosperity Ahead

It didn’t start out like this.

One month into Mr. Trump’s term, the S&P 500 notched a record high. Investors were encouraged by the seemingly unlimited potential of artificial intelligence and a new president who had campaigned on a pro-growth agenda.

Addressing the Future Investment Initiative Institute in Miami on Feb. 19, Mr. Trump assured investors of economic prosperity ahead.

“There’s no better place on earth than the current and future United States of America under a certain president named Donald J. Trump,” he said.

Investors were jubilant. “There was so much optimism in the air,” said Todd Ahlsten, chief investment officer at Parnassus Investments, adding “there were few warning signs on the horizon.”

Within a day of Mr. Trump’s speech, however, worries over inflation started to weigh on the market, intensifying at the beginning of March with the announcement of 25 percent tariffs on Mexico and Canada. Economists expect tariffs, which are a tax on imports paid by the importer, to lead to higher prices for consumers and businesses.

Investors, who once believed that Mr. Trump’s aggressive campaign talk about trade imbalances would not become policy, were suddenly confronting a new reality. The president was serious about imposing tariffs, and he was willing to risk a sell-off in the stock market to achieve his goals.

Investors were still not prepared for what came next.

‘A Huge Change in the Paradigm’

The announcement of double-digit tariffs on countries across the globe incited the worst two-day sell-off for the S&P 500 since March 2020. The difference this time was that the slide came in direct response to government policy.

“It was a rapid sell-off, especially when you consider that there was no external shock like the pandemic,” said Mohamed El-Erian, President of Queens’ College at Cambridge University and the former chief executive of Pimco, one of the largest asset managers in the world.

Economists began sounding the alarm that the economy, which had been experiencing steadily slowing job growth as inflation cooled, was now headed toward a much sharper downturn. The administration again shrugged off the stock slide. Investors rushed to protect their portfolios from further losses.

“The U.S. economy has gone from being celebrated for economic exceptionalism to concerns that it is slipping into stagflation or recession,” Dr. El-Erian said. “That is a huge change in the paradigm for the world’s most important economy.”

The week before the tariffs were expected to go into effect, both the tech-heavy Nasdaq Composite index and the Russell 2000 index of smaller companies — which tend to be more of a barometer of the outlook for the economy than much larger, multinational companies — had fallen into bear markets.

A bear market, in which an index falls 20 percent from its peak, is rare. When one occurs, it is a marker of extreme investor pessimism. In this case, analysts and economists say, it’s over the direction of the economy in response to tariffs. It’s a line in the sand for a sell-off turning into a sustained down market.

When markets closed on April 8 — the day before the tariffs were set to take effect — the S&P 500 had fallen 18.9 percent below its February peak. With the market continuing the fall further toward a bear market as the tariffs came into force the next morning, Mr. Trump announced a 90-day pause for the most punitive tariffs on all countries except China. Stocks rallied, with the S&P 500 recording its best day since 2008.

Alarm Bells Across the Financial System

But it wasn’t the stock market that Mr. Trump said had made him blink.

That same week, something strange occurred in both the bond and currency markets. Typically, in times of turmoil, investors all over the world seek out U.S. assets as a source of reliability and safety. They buy dollars and U.S. government debt, typically pushing up the value of each.

That is what happened as the stock market initially tumbled. But in the days leading up to the tariffs, both the dollar and U.S. government bonds started to fall as well, setting off alarm bells across Wall Street.

Traders described a sense of panic and fear as prices lurched lower, sending yields soaring.

The 30-year Treasury bond started the week with a yield of just over 4.3 percent. In overnight trading before the tariffs went into effect, the yield — which is indicative of the borrowing cost for the U.S. government — rose above 5 percent. That was a huge move in a market that typically moves by hundredths of a percentage point each day.

“The bond market is very tricky,” Mr. Trump remarked

Traders pointed to technical thresholds that were breached in the bond market, setting off a spate of selling from different computer-driven trading strategies that automatically buy and sell based on preset programming.

Then the sell-off gathered momentum, with some analysts saying the unusual moves were a sign that investors were souring on U.S. assets amid the chaos caused by tariffs.

U.S. exceptionalism is rooted in the notion that the United States plays a central role in global financial markets, where the dollar is the reserve currency and the nation’s debt underpins borrowing domestically and internationally. That very notion, analysts say, has become vulnerable.

Amid the chaos, Mr. Trump also ramped up attacks on the people and institutions underpinning U.S. exceptionalism, such as Jerome H. Powell, the chair of the Federal Reserve, whose independence helps underpin investor confidence in U.S. markets.

The president was displeased that Mr. Powell had not lowered interest rates, even though the latter has warned that doing so could fuel further inflation. While many investors also long for lower rates, it is more important to them that the Fed maintain its independence.

More ‘Yo-Yo’ Tariffs?

Since April 9, there had been a shift in the tone of the administration.

Officials have promoted what they say have been positive trade negotiations taking place behind the scenes.

Even when the administration’s claims of talks are rebuffed for being made up, as in the case of China, investors have taken the cue that the White House is trying to give the market something to cheer.

Still, few are willing to bet on what happens next.

One bond banker at a U.S. bank said his team was no longer making trading decisions with a time horizon of up to six months, as it was last year. Instead, uncertainty has forced it to make decisions week to week, with much dependent on the eventual level of tariffs that may not be known for weeks or even months.

Economic data will be watched closely for signs that tariffs are taking hold. Earnings reports will continue to be pored over for signs that tariffs are hitting Main Street.

Then it will be July and the end of the 90-day pause that put tariffs and the market’s meltdown on hold.

“If the administration moderates the tariff policy soon, and the tariff uncertainty abates, the lasting damage might be modest or negligible,” said James Egelhof, an economist at BNP Paribas. He said he was spending an increasing amount of time fielding questions from clients about what a potential economic downturn might look like if the tariff uncertainty persists.

“If we continue on a course where tariffs behave like a yo-yo, going up, then down, then up again, then this uncertainty won’t abate, and it will have a paralyzing effect on businesses in particular,” he said.

Highlighting that uncertainty again on Wednesday, Mr. Trump pushed off blame for the current market turmoil onto his predecessor.

“This is Biden’s Stock Market, not Trump’s,” Mr. Trump wrote on Truth Social. “I didn’t take over until January 20th. Tariffs will soon start kicking in, and companies are starting to move into the USA in record numbers.”

“BE PATIENT!!’ he added.