Fiscalist gezocht voor expat (30%-regeling) voor advies ter voorkoming van dubbele belastingen

Toelichting op de werkzaamheden:
I have 30% ruling, and so is a resident of Netherlands. Also a partial tax resident due to the 30%.

The question is about double taxation relief, and how to fill the United States' W-8 BEN form.

First some background: I hold common stocks of a private company in United States. I received these stocks from my ex-employer when was I in another country.
Now, I have an opportunity to sell these shares to a private buyer, and the money I get will be routed to a Dutch bank. This is a world-wide income.

The question is about double taxation relief using the tax treaty between the US and Netherland.
Because, I want to file the Form W-8 BEN (Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding and Reporting) requesting tax relief from US.
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Deadline: Graag zo spoedig mogelijk