Recordkeeping obligations require dealers to maintain accessible tax records and invoices to enable tax authority verification. Dealers and persons served notices must prepare, maintain and retain sufficient records at their principal place of business to allow the Commissioner to ascertain tax liabilities and explain relevant transactions. Computerised records are acceptable if soft and/or hard copies can be produced. Registered dealers must preserve issued invoice copies, originals of received invoices, and payment challans. The Commissioner may prescribe record form, require specified accounts by notice, and notify classes of persons to keep specified accounts. Records must be retained for the statutory retention period and preserved during pending proceedings; loss must be reported to police and the Commissioner within fifteen days.