This means that you have invested in a US limited partnership through a foreign person who received form 1042-S, or you erroneously signed form W-8 certifying that you are a foreign person. If the former you probably have to file either form 5471, 8865, 8858 for the foreign person who received the form reporting the income withintheentity. If the latter, please contact the issuer and provide them your W-9, which will give you a K-1 to report the partnership income on Sch E of your 1040.
