Guidance for Returning Officers administering a Senedd election

The full name for each party list candidate must be included on the nomination form, surname first, followed by all of their other names in full.1
    
An individual candidate must state their full name on their individual nomination form, surname first, followed by all of their other names in full.2

Prefixes and suffixes

The nomination form does not prescribe a space for prefixes or suffixes.

Candidates and parties should be advised not to use prefixes such as Mr, Mrs, Dr or Cllr, or suffixes such as OBE or MBA as part of their full name. If a prefix or suffix is included as part of the actual name, the nomination form would not be invalid as a result, but the prefix or suffix should not be transferred to the statement of parties and persons nominated.
  
If a candidate has a prefix or suffix as part of their actual name, you should inform the party, individual candidate and their agent that it will not appear on the statement of parties and persons nominated (as appropriate) or the ballot paper, but that their nomination has not been affected.

The only exception to this is where a prefix or suffix has been included as part of a commonly used name and that is how the candidate claims to be commonly known.