I have just taken on a new CIS client and he has outstanding tax penalties and interest from 2004. He says he cannot recall how this happened but looking back on his account it would seem that a tax return wasn't submitted and tax has been determined by HMRC. There are two £100 penalties in 2005 as could be expected, but then a further penalty of £210 in Jan 2008. I remember the £100 penalties if tax is outstanding but not the additional £210. Can anyone shred any light on what this is?