The FA has issued International Clearance guidelines.

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. If the player is under the age of 18, they are subject to the provisions of FIFA Article 19 – please see footnote. International clearance is applicable at all levels of the game.

Further info is available from The FA at this link.