A balance sheet was an accounting document.
In 2374, Kira Nerys believed Quark's assertion that the occupation of Deep Space 9 by the Dominion wasn't so bad was only true if the only thing he cared about was a monthly balance sheet. (DS9: "A Time to Stand")
In 2375, Ezri Dax cited the multitude of contracts, invoices, balance sheets and shipping orders as the reasons why she never went into her family's business. (DS9: "Prodigal Daughter")