I have come across a foreign dividend tax anomaly which I have been unable to resolve by reading the reciprocal tax treaty operative between the USA and the second country,( the Federal Republic of Germany.).

On both the US IRS and the US Treasury web-sites the text of the reciprocal tax treaty with Germany and the formal protocol is available. I have studied the treaty, the protocol and the technical explanations and I have found that the tax treaty rate of withholding tax for dividends payable to individuals in the treaty countries is stated as 15%.
i.e. a US person as defined by the US IRS, normally resident in the USA, and receiving dividends from a German resident company; or a German person, normally resident in Germany, and receiving dividends from a US resident company is assessed withholding tax on the foreign dividend at the treaty rate, not at the local rate.

My US Brokerage insists that the applicable withholding rate for a US person, resident in the USA, receiving dividends from a German resident company stock is 26.37%. Furthermore my brokerage insists that in order to qualify for the treaty withholding rate I must file with the IRS an application for certification as a US resident and then file a copy of the certification with the Brokerage; I have been unable to find the basis for this claim in the treaty documents. I hold a large percentage of my investments in off-shore companies, in several different nations and I have never come across this anomaly with respect to any other country having a reciprocal tax treaty with the USA. To date I have not yet been able to obtain from my brokerage a citation for the reference documents upon which their claim is based.

Please, can anyone shed light on the basis for the claim made by my Brokerage. Thank you for your attention.