overnight usps deadline refers to the latest time a package can be sent for delivery the following day using USPS’s overnight services. For USPS, overnight shipping is typically available through Priority Mail Express, which guarantees delivery the next day or within two days, depending on the destination. The cutoff time for overnight shipping can vary by location, so customers should check with their local post office or use USPS’s online tools to confirm the exact deadline for shipping. Meeting the deadline ensures that packages arrive on time without delay.