Here is how PMB must be addressed henceforth – FG

The Secretary to the Government of the Federation (SGF), Boss Mustapha has issued a circular, instructing all concerned on the proper way to address President Buhari, both at formal events and via correspondence.
The directive, which takes effect immediately, according to the SGF was necessary because there had been inconsistency in the way the number citizen of the country is being saluted.
Mustapha in the memo dispatched to all the ministries, departments and agencies of the federal government wrote:
“Government has observed with concern the inconsistent manner in which the President, Federal Republic of Nigeria is addressed during Official and Private functions. It has therefore become necessary to have a standard format for addressing him at such formal occasions. To this end, Mr. President shall henceforth be addressed as ‘‘MUHAMMADU BUHARI, PRESIDENT OF THE FEDERAL REPUBLIC OF NIGERIA.’’ except in purely Armed Forces Programmes, where “COMMANDER-IN-CHIEF OF THE ARMED FORCES OF FEDERAL REPUBLIC OF NIGERIA” will be added. All concerned persons should accordingly be guided and ensure strict compliance with the contents of this Circular.”
The circular also advised that though the president is a retired major general, he is, however, not to be addressed by that military rank at formal functions.