701—219.16 (423) Liability of subcontractors. A subcontractor who is providing materials and labor on the actual construction of the building or structure has the same status and tax responsibilities as a general contractor under the Iowa statutes. However, where an individual or firm is hired to provide machinery and equipment to a general contractor or another subcontractor, the individual or firm is considered a material supplier rather than a subcontractor. This is true even though the machinery and equipment are supplied with installation. Items of machinery and equipment sold by material suppliers to contractors shall be sold for resale and the contractor must provide the material supplier with a valid resale certificate.