Can a buyer use my own financial statements against me to argue for a lower price?

Yes, this is exactly what due diligence is designed to do — a buyer's accountants and lawyers will comb through your financial statements looking for anything that supports a lower price: declining trends, inconsistent numbers between different documents, unusual or unexplained expenses, or add-backs they don't accept. This isn't improper; it's the normal, expected mechanics of negotiating a business sale, and virtually every buyer's advisor will do some version of it.

The nuance is that being prepared for this is far more useful than being surprised by it. Reviewing your own financial statements critically, ideally with your accountant, before a buyer does, lets you identify and address anything that looks concerning, prepare a clear explanation for anything unusual, and decide in advance which points you're willing to negotiate on and which you're not.

Financial statements that are consistent across documents, well-organized, and accompanied by clear explanations for anything unusual tend to give a buyer far less to work with than a messy or inconsistent set of records. A business lawyer, working alongside your accountant, can help you anticipate the specific arguments a buyer is likely to raise before you're negotiating them under pressure.