Use letters after your name appropriately. For example, writing your university degree (BA Hons or BSc Hons) after your name when writing to friends looks pretentious. But including appropriate professional letters after your name on a business card makes good sense. No letters after the name should be added on invitations, but on formal lists and in professional correspondence they may be included. There is an order of precedence for letters after names.
The abbreviations ‘Bt’ or ‘Bart’ for a baronet, and ‘Esq’, if applicable, come first. These are followed by orders and decorations conferred by the Crown, which have their own order of precedence. Privy Counsellors and Appointments to The Queen are next, followed by Queen’s Council (QC), Justice of the Peace (JP) and Deputy Lieutenant (DL).
University degrees are written subsequently, followed by religious orders and medical qualifications. The next group of letters consists of: Fellowships of Learned Societies, Royal Academicians and Associates, Fellowships, memberships etc. of professional bodies and Writers to the Signet. MP (for Members of Parliament) is penultimate in the order of precedence, followed by letters denoting membership of one of the Armed Forces.