An Act amending the act of March 4, 1971 (P.L.6, No.2), known as the Tax Reform Code of 1971, in personal income tax, further providing for definitions and for income taxes imposed by other states and providing for provisions for overtime pay; in corporate net income tax, further providing for definitions, for determination of net loss deduction, for imposition of tax, for reports and payment of tax, for timely mailing treated as timely filing and payment and for additional withholding requirements, repealing provisions relating to consolidated reports, further providing for extension of time to file reports, for changes made by Federal Government, for limitations on assessments, for definitions, for manufacturing innovation and reinvestment deduction, for enforcement, rules and regulations, inquisitorial powers of the department, for retention of records and for penalties; in tax credit and tax benefit administration, further providing for definitions and providing for application of tax credits or tax benefits to a unitary business; providing for working Pennsylvanians tax credit; and, in general provisions, further providing for estimated tax, for underpayment of estimated tax and for restatement of tax liability under treaties.