Gov and search for withholding requirements for updates, online tools, and more information, including: Forms and Publications A. Nonresident Withholding.It also explains how to fill out the NR4 slip and summary. Perform a complete tax analysis. Tax deposits and Form 941 or Form 944. International Social Security Agreements. 8. The company is usually the party responsible for withholding any required tax when it pays a foreign contractor for services performed in the United States. To cancel your representative's authorization, fill out Form AUT01X, Cancel Authorization for a Representative. Deducting income tax.