No due certificate required or not

Hi -

I and my uncle (distant relative) had few bank transactions in few lakhs for he giving me soft loan and I re-payed most of it.  Due to some differences Now he is asking in cash to re-pay the final installment.  There is no prior agreement b/w him and me.

Now if I do that will I need a No Due Certificate from him ? Is it required on a plain paper or a bond paper ?

If I do not take No Due Certificate - Can he file a civil suite for recovery of the money ?

--Tiru.