Gotcha! Tinkler And Estoppel

Estoppel is the legal principle which says, very broadly, that if you and I have dealings on the basis of a shared but mistaken belief that a particular fact is true, I may in some circumstances be debarred from subsequently asserting that it is untrue.  Its application to Revenue matters has been clarified in the recent Supreme Court decision in Tinkler [2021] UKSC 39.

The facts in Tinkler were of the simplest.  HMRC purported to commence an enquiry into Mr Tinkler's self-assessment tax return.  The enquiry notice was defective because, owing to an HMRC mistake, it was sent to the wrong address and Mr Tinkler never received it.

However, a copy was sent to Mr Tinkler's agent.  No-one noticed the defect and the enquiry proceeded in the express belief on the part of both HMRC and the agent that it was valid.