Although a Court of Arbitration for Sport (Cas) panel reduced the ban to four years on Monday, the 60-year-old Platini said he was stepping down to focus on clearing his name.
Platini and former Fifa boss Sepp Blatter were last year found guilty of financial irregularities and had their original eight-year bans reduced to six years by the Fifa appeals committee.
The pair has maintained that the payment in 2011 was made for consultancy work Platini did for Blatter between 1998 and 2002.