next day postage cost refers to the expense of sending a package with guaranteed next-day delivery. The cost for next-day shipping varies based on the carrier, the weight and size of the package, and the delivery service chosen. USPS offers Priority Mail Express, which guarantees delivery within 1-2 days and is available for a wide range of package sizes. UPS and FedEx also offer next-day delivery services like UPS Next Day Air and FedEx Priority Overnight, but they tend to be more expensive compared to USPS services. Businesses often use next-day postage for urgent shipments and time-sensitive deliveries.