Burden of proof
The onus of proof in penalty cases is on HMRC to show that a relevant default occurred. This means, firstly, that HMRC has to prove the basic facts of the act or omission, whether it be an inaccuracy in a document, failure to make a return, etc. If HMRC fails to prove the basic act or omission, no penalty can be imposed. See also discussion of penalty validity at A4.569.
In some contested penalty cases, the basic act or omission will not be in dispute (although the Tribunal will expect HMRC to prove that there was an omission and valid imposition of a penalty, even if not specifically disputed).
Instead, the case will turn on the second question, namely the taxpayer's degree of culpability (if any). Here the burden