Best judgement: methods of calculation
There is no single or ideal method of calculating arrears in those cases that give rise to a best judgement assessment. The nature of the business and the records maintained, and of course, the Excise regime involved will usually provide an indication to the best approach. There are a number of techniques available that are outlined in the relevant regime guidance. Officers are also recommended to liaise with the Units of Expertise for the regime in question.
Clearly, assessments based on one method and confirmed or supported by means of another are to be preferred.
Remember that the best judgement test applies to the specific assessment in question not any other assessment that you could have made.
If retrospective use of a different representative period or method would have achieved a better result or different arrears this should not upset the assessment on the grounds of best judgement, as long as the representative period or method you did use was reasonable.