I have been self employed for three years. I supplied my UTR N0 to my employer/contractor but never knew I should have had a CIS card/number. My contractor/ employer deducted 20% of my salary and not 30% for 3 years. My accountant when doing my tax return never informed me that I had no CIS N0 and neither did HMRC all this time. Who would be looked at as the guilty party and what would be the consequences? can someone please help. This is a question for a tax person I am assuming.