Marshall is a poduct of the Manchester City Youth Academy, which he joined when he was 11 years old in the 2006/07 season. He signed his first professional contract with them.
In June 2010 he signed for Walsall and then for Conference club FC Halifax Town in June 2012. He then moved up a division joining Stockport County in February 2013. He returned to FC Halifax on the back of their promotion to the Conference National League. He made 39 appearances in the 2013/14 campaign helping the club qualify for the play-off semi-finals, where they were beaten by Cambridge United.He remained a key player in the 2014/15 campaign, scoring three goals in 42 appearances.
Paul signed for National League North Bradford Park Avenue in May 2015. Avenue finishing 14th in their 2015/16 campaign. He the signed for Alfreton Town in October 2016.