Just make sure that you do not make the same mistake again. Then there is documentation that you knew how to do it right and did not. If additional taxes are owed they will usually be paid on the next tax return or a payment schedule will be worked out. It is not a bad idea to have a copy of the Federal regulations at the winery premises. If you do not have a copy you can get one from the nearest General Services Bookstore.
Most major cities have one.
The one in San Francisco is located in San Francisco. You can just call them up and order it over the phone. Honest, that is the name of the book. You need to read Part 4, Wine Labeling, Part 16, Government Warning Statement, and Part 24, winery regulations. Do not even think about letting the winemaker read Parts 55 and 179.