If AD of Registered post is not received, the concerned post office can be asked to :
-supply the delivery certificate, which is supplied by the dept.Many of Head Post Office/Post offices are now connected thru internet and a docket number/complaint number is given instantly and a date is given by whcih the delivery certificate can be collected.The delivery certificate is in the shape of a letter.
-supply the POD in addition to delivery certificate. The POD is run sheet on whcih the postman takes the acknowledgment ( with seal in case of companies). For POD Rs.10/ are charged.
Both can be obtained and are useful.