Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

US citizen sometimes residing in spain, wanting to offer consulting services in Europe, TAXES?
With something this complicated you are going to want to consult professionals. Either a professional with international experience, who will tell you the best tax arrangement overall but might come expensive, or one professional in each country who will optimize for that country. You will have to pay US taxes, and depending on your residency probably some in Spain. Double tax agreements should kick in to prevent you paying tax on the same money twice. You do not have to pay separate 'European' taxes. If you do substantial business in another country you might have to pay there, but one of your professionals should sort it out.