Bank statements. One sort of financial record is a bank statement. Your bank will regularly send a statement containing information showing income (credits) and outgoings (debits) on your bank account.
They're synonyms. Gain is the most general. Attain usually means to reach a goal or milestone (he attained the rank of captain). Obtain usually implies careful planning or some effort to get to the thing or goal. But they have probably something like 80% overlap in meaning.
Definition of achieve. achieved. ; achieving. transitive verb. 1 : to carry out successfully : accomplish achieve a gradual increase in production. 2 : to get or attain as the result of exertion : reach achieved a high degree of skill achieved greatness. intransitive verb. : to attain a desired end or aim : become successful.