147.Section 100 provides for the exemption from postal charges for certain petitions and addresses forwarded or sent to Her Majesty, or to the Secretary of State for Northern Ireland, or sent to a member of either House of Parliament, the Scottish Parliament (or its Clerk), the Northern Ireland Assembly or of the Welsh Assembly. It also limits the amount of postage that the universal service provider may recover for the delivery of parliamentary proceedings.
Commentary on Sections Part VI Universal Postal Service: Supplementary Section 100: Certain exemptions from postage etc.