The difference between a taxable purchase of computer software and nontaxable charges for the service of software production for use of the employer are explained in a recent sales and use tax ruling. The billing method or invoicing may not aid in the distinction between taxable sales of computer software and nontaxable charges for personal employee services, so instead a written agreement between the company and the temporary service provider containing certain provisions may be used to establish correct taxability. (Revenue Ruling, 1-02-1, Docket No. 1-02-1)