Is sale agreement necessary for a transfer plot?

I purchased an un-leased plot (transfer) 3 years back in a society in scheme 33, karachi. I did not have information about the process of sale and purchase at that time. I just found out that i don’t have the sale agreement (between me and the seller) in my records. I just have a mutation certificate and the original allotment letter. Is this ok? Was sale agreement necessary?

IMO if you have the allotment letter then it shouldn’t be an issue , it often depends on society requirements