An Act amending the act of March 4, 1971 (P. L. 6, No. 2), known as the "Tax Reform Code of 1971," shifting the burden of proof from vendors to the Department of Revenue on questions concerning the utilization of exemption certificates; eliminating the split second quarter for filing of sales tax returns; reducing the personal income tax rate; permitting the equitable adjustment of taxes and penalties; revising the provisions relating to net loss carryover; adding a definition of "taxable year"; providing a processing exemption for computer software from the capital stock and franchise tax; providing an investment credit; eliminating tentative payments for corporate net income taxes and requiring the payment of estimated taxes; reducing tentative tax payments for the capital stock and franchise tax; changing the time period within which petitions for refunds may be filed; making repeals; and making an appropriation.