The instructions for the Form 8802 state that certification is available for the following:
Purpose of Form
Form 8802 is used to request Form 6166, a letter of U.S. residency certification for purposes of claiming benefits under an income tax treaty or VAT exemption. You cannot use Form 6166 to substantiate that U.S. taxes were paid for purposes of claiming a foreign tax credit.
You cannot claim a foreign tax credit to reduce your U.S. tax liability with respect to foreign taxes that have been reduced or eliminated by reason of a treaty. If you receive a refund of foreign taxes paid with the benefit of Form 6166, you may need to file an amended return with the IRS adjusting any foreign tax credits previously claimed for those taxes.
Who Is Eligible for Form 6166
In general, under an income tax treaty, an individual or entity is a resident of the United States if the individual or entity is subject to U.S. tax by reason of residence, citizenship, place of incorporation, or other similar criteria. U.S. residents are subject to tax in the United States on their worldwide income. An entity may be considered subject to tax on its worldwide income even if it is statutorily exempt from tax, such as a pension fund or charity. Similarly, individuals are considered subject to tax even if their income is less than the amount that would require that they file an income tax return.
In general, Form 6166 is issued only when the IRS can verify that for the year for which certification is requested one of the following applies:
You filed an appropriate income tax return (for example, Form 1120 for a domestic corporation),
In the case of a certification year for which a return is not yet due, you filed a return for the most recent year for which a return was due, or
You are not required to file an income tax return for the tax period on which certification will be based and other documentation is provided.