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HMRC internal manual

Inheritance Tax Manual

Investigating no-grant cases: what to do when you receive an account

You should follow the normal instructions for investigating an account and you should seek a penalty for a late account (IHTM36021) in appropriate cases.    

In addition you should find out, if this is not already clear, why the account was not delivered when it should have been or why a grant was not taken out.  There could be many reasons for this ranging from a deliberate attempt to evade or defer the payment of tax, to a family dispute, genuine ignorance of what was required or simply someone who is not able to cope with the whole process.  The extent of your investigation will to a large extent depend on the explanation.