The Scot's behaviour has come under scrutiny this week after video emerged of an exchange with BBC journalist Vicki Sparks following the 0-0 draw with Burnley on March 18.
He has apologised, and Sunderland issued a statement on Tuesday stating their commitment to Moyes but agreed that his suggestion he might slap the reporter was "wholly unacceptable".
The FA contacted the club on Monday seeking observations about the matter and had wanted a response by the close of business on Thursday.
However, Press Association Sport understands the governing body has granted Sunderland's request to extend the deadline, and they now have until April 10 to respond - the day after the embattled Black Cats host Manchester United
Source : PA
Source: PA