How do you determine if a package requires additional postage?

Determining whether a package requires additional postage primarily involves measuring its weight and dimensions. This is crucial because postage rates are often based on both the weight of the package and its size. If a package exceeds standard weight limits or dimensions for the postage class selected, additional postage will be necessary. For example, a standard letter may have a different rate compared to a large or irregularly shaped parcel that could fall into a higher pricing tier due to its size or bulk.

While other options, such as checking the address or using a postage calculator, can provide some relevant information, they do not directly address the fundamental requirement for determining if extra postage is needed. Visiting a local post office may offer assistance and information, but initially, the measurement of weight and size is a definitive method to calculate if additional postage is necessary.