CH93400 - Penalties for VAT and Excise Wrongdoing: Types of wrongdoing: Level of proof
You must always clearly establish why a penalty is due from the facts.
You must also consider whether the taxpayer has established that there is a reasonable excuse for the act.
Although we accept that proceedings for certain penalties are criminal for the purpose of Article 6 of the European Convention on Human Rights, see CH300000+, the civil standard of proof continues to apply to such cases. This standard of proof is the balance of probabilities.
This means that if the act is non-deliberate you must have sufficient evidence to show that the act occurred and when. If the act is deliberate you will also need sufficient evidence to show that the act was, on the balance of probabilities, deliberate. The quality of evidence should be higher for the more serious behaviour.