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What standards should I expect of my CPA when an error was made?
What is the right way to handle this? Did you check the forms? Did the form state $0 tax due on the FTB LLC/Corp form (I'm guessing you operate as LLC/Corp, since you're dealing with the Franchise Tax)? The responsibility is ultimately yours. You should cross check all the numbers and verify that they're correct. That said, if the CPA filled the forms incorrectly based on your correct data - then she made a mistake and can be held liable. CPA filing forms from a jurisdiction on the other end of the country without proper research and knowledge may be held negligent if she made a grave mistake. You can file a law suit against the CPA (which will probably trigger her E&O insurance carrier who'll try to settle if there's a good chance for your lawsuit to not be thrown away outright), or complain to the State regulatory agency overseeing CPAs in the State of her license. Or both. Am I wrong for expecting the CPA should have properly filled out and filed my taxes? No, but it doesn't shift the responsibility from you. How can I find out if the CPA has missed anything else? Same as with doctors and lawyers - get a second opinion. Preferably from a CPA licensed in California. You and only you are responsible for your taxes. You may try to pin the penalties and interest on the CPA if she really made a mistake. California is notorious for very high LLC/Corp franchise tax (cost of registering to do business in the State). It's $800 a year. You should have read the forms and the instructions carefully, it is very prominent. It is also very well discussed all over the Internet, any search engine would pop it up for you with a simple "California Franchise Tax for LLC/Corp" search. CA FTB is also very aggressive in assessing and collecting the fee, and the rules of establishing nexus in CA are very broad. From your description it sounds like you were liable for the Franchise tax in CA, since you had a storage facility in CA. You may also be liable for sales taxes for that period.