sourced 50% based on title passage and 50% based on location of production and certain assets; c) other gains are sourced based on the residence of the seller. In specific cases, the tax system may diverge for different categories of individuals. U.S. citizen and resident alien decedents are subject to estate tax on all of their assets, wherever situated. The nonresident aliens are subject to estate tax only on that part of the gross estate which at the time of death is situated in the U.S. Another significant distinction between U.S. citizens/RAs and NRAs is in the exemptions allowed in computing the tax liability. Where differing characterizations of an item of income can result in differing tax results, it is necessary to determine the characterization. Some systems have rules for resolving characterization issues, but in many cases resolution requires judicial intervention. Note that some systems which allow a credit for foreign taxes source income by reference to foreign law. Definitions of income Some jurisdictions tax net income as determined under financial accounting concepts of that jurisdiction, with few, if any, modifications. Other jurisdictions determine taxable income without regard to income reported in financial statements. Some jurisdictions compute taxable income by reference to financial statement income with specific categories of adjustments, which can be significant. A jurisdiction relying on financial statement income tends to place reliance on the judgment of local accountants for determinations of income under locally accepted accounting principles. Often such jurisdictions have a requirement that financial statements be audited by registered accountants who must opine thereon. Some jurisdictions extend the audit requirements to include opining on such tax issues as transfer pricing. Jurisdictions not relying on financial statement income must attempt to define principles of income and expense recognition, asset cost recovery, matching, and other concepts within the tax law. These definitional issues can become very complex. Some jurisdictions following this approach also require business taxpayers to provide a reconciliation of financial statement and taxable incomes. Deductions Systems that allow a tax deduction of expenses in computing taxable income must provide for rules for allocating such expenses between classes of income. Such classes may be taxable versus non-taxable, or may relate to computations of credits for taxes of other systems (foreign taxes). A system which does not provide such rules is subject to manipulation by potential taxpayers. The manner of allocation of expenses varies. U.S. rules provide for