How do I file a subcontractor supplemental worksheet with a CSV file for my business taxes? You can find instructions on how to do this on our website here. April 16, 2019 14:13 Related articles How do contractors deduct payments made to subcontractors on their business tax return? How do I file business tax online? Business Tax Classification 4 - for Contractors How is substantial nexus defined for business tax purposes? How do I upload a CSV file with my business tax return in TNTAP?