For anyone self employed in the UK, the IR35 rule is something to be aware of – as falling "in" IR35 can cause a huge tax liability. The HMRC has published a guidance PDF with a scoring method to establish where you stand. The PDF is here, the source page is below. HM Revenue & Customs: IR35 – Countering Avoidance in the Provision of Personal Services. Source article with more background: http://www.contractoruk.com/news/0010548new_ir35_guidance_unveiled_hmrc.html