A sales tax deficiency determination is conclusion reached by the Board of Equalization (BOE) of California that the business owner owes more taxes than he reported. Rev. & Tax Code 6481 provides that the Board may “compute and determine the amount required to be paid upon the basis of the facts contained in the return or returns or upon the basis of any information within its possession or that may come into its possession.” In other words, the Board is permitted to “go behind” the business owner’s books to confirm factually what the actual liability should be.