I look after the admin for my local community club 1st team. You can't play in the 1s league games if you are not registered for the club. You have to start a game with 4 FR capable players. You are allowed 100 registrations, and my instructions when taking on the job was if they were FR capable and lived within 100 miles, register them; and don't deregister them until they are 55 (well just a bit facetious)
Late registrations to play the coming weekend, and the RFU can/will charge £45 (almost as much as my membership fee) for a late transfer. They, as well as ECC, love making it easy for (community) clubs.......