This two-part report on tax expenditure programs (TEPs) is the. fourth in a series of such reports produced by the Legislative Analyst's Office. The initial reports were prepared in response to Resolution Chapter 70, Statutes of1985 (ACR17,Bates). Tax expenditure programs, as defined by ACR 17, include various tax exemptions, exclusions, deductions, credits, and other special tax provisions which affect the ammmt of revenues collected through the state's tax system. The term "tax expenditure" generally has been used to define programs which result in exceptions to the "basic" tax stmcture of the state. As we discuss this part of this report, considerable differences of opinion exist regarding the definition of the term basic tax struchue, and thus, what constitutes an exception to this base.