(a) The rules in this part implement provisions in 39 U.S.C. chapter 36, subchapter I, establishing the modern system of ratemaking for regulating rates and classes for market dominant products. The rules in this part are applicable whenever the Postal Service proposes to adjust a rate of general applicability for any market dominant product, which includes the addition of a new rate, the removal of an existing rate, or a change to an existing rate. Current rates may be found in the Mail Classification Schedule appearing on the Commission's website at www.prc.gov.

(b) Rates may be adjusted either subject to the rules appearing in subpart B of this part, which includes a limitation on rate increases, or subject to the rules appearing in subpart I of this part, which does not include a limitation on rate increases but requires either extraordinary or exceptional circumstances. The rules applicable to the calculation of the limitations on rate increases appear in subparts C through H of this part. The rules for workshare discounts, which are applicable whenever market dominant rates are adjusted, appear in subpart J of this part.