The United States will levy a 10% import surcharge on most goods from 24 February after President Donald Trump signed a proclamation under Section 122 of the Trade Act of 1974. The White House says the measure will run for up to 150 days, applies from 12:01 a.m. Eastern, and carves out exemptions for certain critical minerals, energy products, pharmaceuticals, specified electronics and a range of passenger vehicles. Goods qualifying for duty‑free treatment under USMCA remain outside scope. (whitehouse.gov)

The move follows a 6–3 US Supreme Court ruling that the administration exceeded its authority by using the 1977 International Emergency Economic Powers Act (IEEPA) to impose sweeping tariffs. The President criticised the decision and immediately signalled he would turn to other statutes to keep tariffs in play. (apnews.com)

Section 122 is a balance‑of‑payments tool that non‑partisan Congressional researchers note had never previously been invoked; it caps surcharges at 15% and limits them to 150 days unless extended by Congress. Friday’s proclamation marks its first real‑world test. (congress.gov)

For UK firms, scope is the immediate question. The White House lists exemptions in broad product terms rather than HS‑line detail, and Canada and Mexico retain carve‑outs where USMCA confers duty‑free status. UK exporters, not covered by USMCA, should assume the 10% applies unless an exemption can be evidenced at tariff‑line level. (whitehouse.gov)

Other US trade duties remain. Product‑specific levies under Section 232 (national security) and Section 301 (unfair practices) are unaffected by the Supreme Court decision, so existing rates on items such as steel, aluminium and some autos still apply alongside-or instead of-the new surcharge, depending on the category. (goodwinlaw.com)

Markets took the ruling in their stride. On Friday 20 February, the S&P 500 closed up 0.7%, the Dow rose 0.5% and the Nasdaq gained 0.9%, a sign investors had partly priced in both the court’s move and a pivot to alternative tariff tools. (apnews.com)

Exposure for the UK is significant. ONS data show the US was the UK’s largest goods export market in 2024 at £59.3bn, while services exports reached £137bn. Top goods categories included cars, machinery and pharmaceuticals, with scientific instruments also prominent. (ons.gov.uk)

The sensitivity has been evident in recent prints: UK goods exports to the US fell by £2.0bn in April 2025-the sharpest monthly fall since records began in 1997-with ONS attributing the drop to US tariff measures. Automotive, chemicals and metals bore most of the strain. (ons.gov.uk)

On the new 10% duty, sector cross‑currents matter. Passenger vehicles and certain parts appear on the exemption list, as do pharmaceuticals and some electronics-supportive for segments of UK industry-but the headings are wide. Finance teams should confirm tariff‑line treatment before assuming relief. (whitehouse.gov)

Refunds from the now‑illegal IEEPA tariffs will take time. The Wall Street Journal estimates roughly $133bn had been collected and notes the Supreme Court left mechanics to the Court of International Trade. One dissenting justice warned the process could be messy-signalling lengthy timelines for any repayments. (wsj.com)

The macro read‑across is not trivial. KPMG modelling last year suggested sustained US tariffs could hold UK GDP growth near 0.8% in 2025–26, while a British Chambers of Commerce snap poll found 62% of UK firms with US exposure expected a negative impact, with a third planning price increases. That frames the downside if a 10% baseline becomes a rolling feature. (kpmg.com)

What to do now: UK exporters should re‑price open quotes for US customers, verify Incoterms where the seller is importer of record, and align with customs brokers on whether consignments departing this weekend will present at the US border before or after the 12:01 a.m. Eastern cut‑over on 24 February. Update landed‑cost models, revisit promotional calendars, and prepare variant pricing that toggles the surcharge on and off by SKU.

Two watch points sit ahead. First, whether Congress extends the measure beyond the initial 150 days-without that, Section 122 lapses. Second, whether the administration leans harder on Section 232 or 301 investigations to entrench higher tariffs on targeted sectors or countries. Both risks feel live for Q2. (congress.gov)

For investors, the message is practical rather than dramatic: tariff headlines can change overnight; company pricing and supply chains cannot. Expect choppier earnings guidance for UK mid‑cap industrials, chemicals distributors and auto suppliers with high US exposure, while pharmaceuticals and parts of electronics may see partial relief if exemptions hold in customs practice.