Follow the link to FA site for ICT guidelines. Read more at http://fulltime-league.thefa.com/DisplayNews.do?noticePlacementID=952138837¬iceID=193310111&league=479698#wIO1ku9gVEcTBl1B.99

In accordance with FIFA Regulations, international clearance is required for any player over the age of 10 who is seeking to register for a club in England and has previously been registered for a club abroad (including the other Home Associations), or who is a foreign national seeking to register for the first time in this country.

FA Standard Code of Rules - 18 (b) (i) also refers

http://www.thefa.com/football-rules-governance/policies/player-registration/international-clearance
Read more at http://fulltime-league.thefa.com/DisplayNews.do?noticePlacementID=952138837¬iceID=193310111&league=479698#wIO1ku9gVEcTBl1B.99