City were charged for failing to ensure anti-doping officials knew where their players were for drugs testing. Clubs are required to provide accurate details of training sessions and player whereabouts so that they are available for testing at all times. City were given until 19 January to respond but now have until 16:00 GMT on Friday, 27 January.
The club has allegedly failed to ensure its information was accurate on three occasions, leading to the FA charge. It is understood the information was not updated following a change to training routines. The FA operates a 'three strikes' policy for such breaches, for which the most likely punishment is a fine.