M also includes basic standards for documentation. The P module contains the procedures for paying postage. Verified Drop Shipment, and First Class or Standard Mail Mailings with Different Payment Methods. This module also describes how to obtain refunds for postage, value added refunds, and how to exchange postage stamps. This module contains the prices for products and services offered by the Postal Service.
R is the only module that contains prices.
The S module explains the indemnity claims process, money orders, and the special mail services available to customers. This module contains a summary of recent changes to the DMM and includes an index of subjects. The basic division of the DMM is the unit, identified by an alpha and three digits. Each unit presents a set of standards on a particular topic. The first digit of a unit number represents one of eight broad categories.