The declaration in Form 12A shall he furnished by a dealer before the audit or the appropriate auditing authority or the assessing authority at any time on or before the date of hearing for audit under section 43 or assessment under section 46, or section 48 by such authority:

Provided that if the appellate or revisional authority is satisfied that the dealer concerned was prevented by sufficient cause from furnishing such declaration within the time as aforesaid, before the appropriate assessing authority, such appellate or revisional authority may, for reasons to be recorded in writing, allow the dealer to furnish such declaration up to the time of hearing of appeal or revision, as the case may be.