Transfer of share certificate

Hi All, My husband had purchased the flat in the year 2008 from his own elder brother who was a member of our co-operative housing society having a share certificate. For housing loan we were asked by the bank to get NOC from the said society. As per CHS bye-laws the elder brother was asked to pay the transfer premium or the goodwill amount of ₹25,000/- to the society before they issued him NOC to sell his flat to us. NOC was issued but till date the society haven't transferred the share certificates in my husband's name. Today we want to sell the flat and we are been asked by the prospective buyer whether we have our share certificate in our name. My question is 'is it necessary for us to get get the share certificates transferred in our name?' OR 'Can we ask the society to transfer the same in our prospective buyer's name once we get the sale agreement done and registered in their name?' Also if the share certificate is transferred now in my husband's name do we have to wait for one year period to sell off my said property?..please give me reply on urgent basis what should I follow?? Thank you to all in advance.