Tax deduction certificates: mandatory Form 16 format, issuance timelines, duplicate certificate procedure and AO verification required. The amendment replaces rule 31 to require TDS certificates to be issued in prescribed Form No.16 printed and serially numbered in government-supplied books on application in Form No.17, with a waiver for computerized companies; it prescribes issuance timelines for different payment types, permits duplicate certificates on plain paper when originals are lost, and requires AO certification and an indemnity bond before granting credit on duplicates, while substituting Forms 16 and 17 and omitting specified other forms.