Business profits taxation: permanent establishment profits taxable in host state only to the extent attributable to that establishment. Profits of an enterprise are taxable only in the State of residence unless business is conducted in the other State through a permanent establishment, in which case only profits attributable to that permanent establishment may be taxed there. Attribution follows the separate and independent enterprise principle, allowing deductions for expenses incurred for the permanent establishment subject to the host State's tax law. Customary apportionment methods remain permissible if consistent with this Article. No profits are attributed merely for purchases of goods. Attribution methods should be applied consistently year to year unless good reason exists, and income covered by other Articles remains governed by those Articles.