A bank account was a personal repository for one's money in a bank.
In 2370, Vaatrik Pallra received deposits of 100,000 Bajoran litas in her bank account from various Bajorans she had never contacted before, whose names were on a stolen list. Odo, upon learning of this, suspected she was blackmailing them about being collaborators with the Cardassian Union during the Occupation of Bajor. (DS9: "Necessary Evil")
In 2373, after Quark expressed his disgust at the Regent of Palamar's bloodthirsty plans for the Palamarian Freedom Brigade, calling the man insane, Gaila retorted, "Stop being so judgmental. It's his bank account, not his mental health you should be concerned with." (DS9: "Business as Usual")