Essential codes include: ISWC (International Standard Work Code) - unique identifier for your composition, generated after PRS registration. CAE/IPI number - your personal identifier as a writer, issued when joining PRS. For recordings: ISRC (International Standard Recording Code) - unique per recording, obtained from PPL or distributors. Publisher codes if applicable. Society member numbers for all territories where you're registered. These codes ensure accurate tracking and payment across global systems. Always include ISWCs on cue sheets and in metadata. Keep a master spreadsheet of all codes. Incorrect or missing codes are the primary cause of lost royalties.