The WBO could strip Tyson Fury of his heavyweight world title unless he responds to a notice from chairman Luis Batista-Salas within 10 days.
Fury has until October 17 to notify the WBO "why his title should not be vacated due to inactivity, breach of contract and performance-enhancing drugs and stimulants."
The undefeated Mancunian was due to defend his WBA and WBO belts against Wladimir Klitschko on October 29, but the fight was called off for a second time after his management team declared he was "medically unfit to fight".
Fury's uncle and trainer, Peter, told BBC Radio 5 Live on Sunday that the 28-year-old is "happy for the belts to be freed", as long as the boards can put him as champion in recess.
The British Boxing Board of Control (BBBofC) is meeting on October 12 to look at Fury's admission that he took cocaine, which was made during an interview with Rolling Stone magazine, and is expected to make an announcement regarding his boxing licence within 24 hours.
The letter from Batista-Salas to Fury said: "The WBO Championship Committee decided that you have ten (10) calendar days, final and non-extendable to show cause why your title should not be vacated due to inactivity, breach of contract and performance enhancing drugs and stimulants."
Batista-Salas also said he was concerned for Fury's "health, well-being, happiness and prospects for a full and complete recovery".