United Parcel Service Inc. suffered its biggest one-day share drop after shocking the market by slashing business with the world’s largest online retailer.

United Parcel Service will halve its Amazon package volume to bolster its profitability, but the unexpected move sent the stock tumbling Thursday. Why it matters: UPS gets nearly 12% of its revenue from Amazon deliveries,

United Parcel Service on Thursday forecast downbeat 2025 revenue as it cuts back deliveries for its largest customer, Amazon.com , and grapples with stubbornly soft demand for lucrative overnight service and commercial shipments.

United Parcel Service Inc. shares plunged after the company projected annual revenue well below expectations, telling investors that a long-awaited rebound in demand for its parcel services won’t arrive this year and prompting it to slash its low-margin business with Amazon.

UPS CEO Carol Tome said on a call with investors that Amazon is UPS’ largest customer, but it is not the company’s most profitable customer.