Ive just finished a contract for a large well known housing development and if your going inside to clean you will definately need a cis card.
Takes about 5 days to arrive but its worth having.
Outside cleans are exempt from cis
P.s next year its all changing again and you wont need a cis card/certificate as it will be down to each individual to do their own tax deductions atter payment builders cleans or not.