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.
achieve. 1  to bring to a successful end; carry through; accomplish: The police crackdown on speeders achieved its purpose. 2  to get or attain by effort; gain; obtain: to achieve victory. 3  to bring about an intended result; accomplish some purpose or effect.