All domestic corporations (those chartered in North Carolina) and all foreign corporations which are doing business in North Carolina and every inactive corporation chartered or domesticated here must file an annual franchise and income tax return using the name reflected on the corporate charter if incorporated in this State, or on the certificate of authority if incorporated outside this State. A franchise tax is imposed on corporations for the privilege of doing business in this State even though the activities are exempt from income tax under P.L. 86-272. For a corporation that is subject to both income tax and franchise tax, its apportionment factor is the same for both taxes. For a corporation that is subject to franchise tax but not income tax, its apportionment factor for computing the amount of franchise tax due is the same factor that would be used if its activities that are protected by P.L. 86-272 were subject to income tax in this State.