I think you folks are confusing each other with this discussion of 'where' you're forming this partnership.I believe that a partnership that is engaged only in the investing in stocks and bonds can be formed by a telephone conversation between the partners, or a written document, if you'd like a record of what you're agreeing to.The partnership is not 'formed' in one state or another, it simply exists. It is not 'doing business' in any state, in the context of the need to register anywhere as a foreign partnership. If you think you need a domicile, then that would be where the managing partner is located.And don't further confuse the issue by considering a limited partnership. An LP does have to file a certificate of formation with a state, and file annual reports, etc., etc. But there's no need to limit anyone's liability if you're only investing in stocks.