Umpires must use all the available tools for control which helps to maintain discipline within a match. This is generally using the Green, Yellow and Red card system of warnings and suspensions as appropriate. Guidance is available within the FIH Rules of Hockey in this connection.
If a red card/MMO is issued during/after a match, then the procedures for reporting this must be followed in accordance with England Hockey’s guidance:

Red Cards And Matchday Misconduct Offences (MMO’s) (englandhockey.co.uk)