overnight letter cost depends on the carrier, delivery destination, and package size. Major courier services like UPS, FedEx, and USPS offer overnight letter delivery options, but the cost can vary based on the urgency of the delivery and the shipping method chosen. For instance, UPS offers Next Day Air services, while USPS provides Priority Mail Express for overnight delivery. FedEx also offers similar services such as FedEx Standard Overnight, which guarantees delivery by the next business day. The cost of sending an overnight letter typically includes the base rate for the delivery service, as well as any additional charges for weight, dimensions, and delivery area. The more urgent the delivery, the higher the cost tends to be, especially for services like UPS Express Critical or FedEx First Overnight. Overnight letter services are often used for time-sensitive documents and parcels that need to be delivered quickly and securely. It’s important to compare the rates and services of different carriers to find the best option for your needs, especially if you are shipping valuable or important documents.