Best judgement: record of decision making
When you make an assessment you must maintain records to support your decision. This is extremely important, as the person to whom the assessment is notified may appeal against it and you may have to explain your decision to the tribunal. You do need to have sufficient information to justify your decision and this information must on the balance of probability support the best judgement assessment.
Once you have calculated the arrears to best judgement, you should ask yourself is this figure credible? Could the business have actually under-declared this amount of duty.
The tribunal will consider the above questions. If the amount you calculate does not pass the credibility test then your assessment may not be to best judgement. Ensure you have given enough consideration to all the facts and evidence.