A North Carolina taxpayer who entered into optional maintenance agreements with customers on a cost-per-copy basis was not liable for sales tax. Since the cost-per-copy optional maintenance fee charged by the customer did not represent the sale of tangible personal property, the State concluded that there was no substantial difference in the traditional maintenance agreements and the cost-per-copy agreement, and therefore exempt from tax. The Department also concluded that the optional maintenance agreements used by the taxpayer constituted the furnishing of turnkey services for consideration based upon the number of copies produced. However, the taxpayer was liable for tax on the cost of the parts, supplies and materials used by the taxpayer in fulfilling the maintenance agreements. (Secretary of Revenue Decision, No. 2007-14, North Carolina Department of Revenue)