For years my accountant had me add up all my sales & all my write offs and off that they would determine what I owe for taxes(payroll, sales & federal/state taxes). Because of that the IRS saw a mistake so I was audited for 2 years at once. My accountant then had told me to get quickbooks & finally checked my bank statements. That is where they had found extra sales but also a lot more write offs. I had owed an extra $8k to IRS and the accountant charged me $8300. According to new accountant the old accountant can be found on malpractice and over billing. His suggestion was to sue him because it was his duty to protect me and to teach me correct book keeping. And to make sure my sales were correct by checking my bank statements. I was adding up everything by every receipt and every check I wrote. So there were a lot of errors found.
You may consider a malpractice lawsuit, if facts so justify. The best first step is an Initial Consultation with an Attorney. You can read more about me, my credentials, awards, honors, testimonials, and media appearances/ publications on my law practice website. I practice law in CA, NY, MA, and DC in the following areas of law: Business & Contracts, Criminal Defense, Divorce & Child Custody, and Education Law. This answer does not constitute legal advice; make any predictions, guarantees, or warranties; or create any Attorney-Client relationship.
