How maintain the TransationLog ?..

HI Friends,

          Recently i have done Accounts Project.In that i don't done any Transation Log for any updation.Thats need for client in case of any moral activities.

          I would have to track who done that transation , when , howmuch and for which id These information have to be track clearly.

         How should i do  professtionally ,Guide me 


Thanks in Advance ,

-Ernesto Karthik