i think i had to got to a tax office .mine was in Hertford in Herts and just told them i needed to be cis registered to get some work through various people and then they helped me fill the form out . just dont tell them that you have already done any work with out a card .........or they will ask how you were going to declare the tax

they kept trying to catch me out , especially as i had a shirt on with the geezers name who id been working for wriote all over it i just told them id only just pick it up ready to start the next day . !!