  I have read the It's an Honour site quite thoroughly and I may just be stupid, but I do not see how there could ever be a prescription along the lines of, 'You must always include all post-nominal letters to which you are entitled after your name', which is what I was trying to say when I said that it is up to the individual's discretion. For example, a close friend of mine is entitled to use the DSO post-nominals after his name, but he does not always do so as he feels it is not always appropriate. Further, he has many ribbons he is entitled to wear, but, in situations that call for ribbons, he does not always wear all of them. You did not point me to any rule stating which may be worn, only a list of those which have a particular precedence (and vague rules for foreign awards). Thus, as there is no rule saying you must always use all your entitled post-nominals, the fact that General Cosgrove did not use CNZM is not evidence that he could not.  Again, I read the references, but did not see any rule saying that post-nominal letters cannot be used unless authorised by the GG. It indicates that there are awards Australians may not accept (and may not wear), but does not say that it is an exhaustive list. CNZM is obviously an award Australians may accept, as several have. It also obviously does not have a specific precedence, but I have not been able to find any information indicating that Australians may not use its post-nominal letters.   