There is also the practice of 'frocking' an officer who is assigned to a position that requires a higher rank (there are a number of reasons this might be so), but who has not yet been promoted to that rank. Officers who are selected for promotion still have to 'wait their turn' according to their seniority, so that two people promoted by the same board will not flip-flop in terms of seniority. There can be a waiting period (as long as a year) while an officer may be 'Promotable' yet not yet actually promoted (or receiving the pay for their new rank). During that time frame, they are entitled to add a (P) after their current rank (e.g., 'MAJ (P)'). They may also be assigned to a position requiring the higher rank (and thus, tying back to my first point, need to be 'frocked').