Replacement prefixes are special letter codes used when a damaged or misprinted banknote needs to be replaced during printing. Instead of reprinting the same serial number, the printer uses a different prefix to show that the note is a replacement. This helps with tracking and record-keeping. These replacement notes are less common because most notes pass quality checks and don’t need replacing. That’s why collectors often find them more interesting. For the older Orchid and Bird series, replacement prefixes were always Z1, Z2, Z3, or Z4. But for the Ship, Portrait, and Commemorative series, the prefixes are more varied—examples include Z1, ZZ, and RA for Ship notes, and 0WV, 0CX, and 0PK for Portrait notes.