Where a re-examination of an assessment under Finance Act 1997 Schedule 5 paragraph 14, 15 or 17 indicates that it should have been made for a greater amount, paragraph 18 of the Schedule allows a supplementary assessment to be made.
This is provided that the assessment is made under the same paragraph as the original assessment and the time limit applicable to the original assessment has not expired.
The making of supplementary assessments does not involve new evidence of facts. An assessment under, paragraph 18 of the Schedule is based on the same facts as the original and is made only where the judgement applied to those facts remains unchanged.
For example: A supplementary assessment may be made where an arithmetical error is discovered in an officer’s calculation or schedule, perhaps a figure has been omitted or figures transposed, but the basis of the assessment remains the same, therefore the original assessment is not fundamentally flawed.