usps next day delivery late refers to situations where a package that was scheduled to be delivered via USPS Priority Mail Express or another next-day service experiences a delay. USPS guarantees next-day delivery for Priority Mail Express in most locations, but sometimes, due to weather, high package volume, or other factors, the delivery may be delayed. In these cases, USPS typically offers a refund for the shipping cost if the package is not delivered on time. Tracking updates and customer service can help clarify the situation.