Farrell cleared for England's Six Nations opener despite ban
Farrell escaped any on-pitch punishment in last Friday's match after his shoulder made contact with the jaw of Jack Clement but after he was cited for "dangerous tackling".
"Farrell accepted foul play but challenged that it met the red card threshold, however, the panel upheld the charge and Farrell received a four match ban," the RFU said in a statement.
The RFU added that the four-match ban will be reduced to a three-week ban if Farrell completes the World Rugby Coaching Intervention Programme.
The three-week ban means he will miss two European and one Premiership match for Saracens but frees him to play for England against Scotland and Italy on February 12, both at Twickenham.