How do I file a subcontractor supplemental worksheet with a CSV file for my business taxes? Instructions for filing subcontractor information via a CSV file can be found here . January 24, 2020 16:31 Related articles How do contractors deduct payments made to subcontractors on their business tax return? How do I upload a CSV file with my business tax return in TNTAP? Business Tax Classification 4 - for Contractors How is substantial nexus defined for business tax purposes? How do I file business tax online?