An ad hoc rate is a special rate that is provided by a carrier on short notice. It is typically used for shipments that are not part of the carrier's regular schedule or for unexpected and urgent shipments. These rates may be higher than regular rates, as they are designed to account for the additional costs and resources required to handle an ad hoc shipment. They are usually negotiated on a case by case basis and are typically used for ad-hoc delivery, unexpected or urgent shipment. It's important to note that this type of rate will vary depending on the carrier or logistics company you are working with.