148.020.  Definitions. — For the purposes of this law the following terms shall have the following meanings:

  (1)  The term "banking institution" means every bank and every trust company organized under any general or special law of this state and every national banking association located in this state and any branch or office physically located in this state of any commercial bank or trust company;

  (2)  The term "director" means the director of revenue in charge of the state department of revenue;

  (3)  The term "director of finance" means the chief officer of the present state division of finance, or of such agency of the state of Missouri as may hereafter have by law the supervisory duties of the present state division of finance pertaining to banks and trust companies incorporated under the laws of this state;

  (4)  The term "income period" means the calendar year or relevant portion thereof next preceding the taxable year;

  (5)  The term "lease or rental of tangible personal property" means the lease or rental of tangible personal property under the exclusive control of the lessee and neither attached to nor functionally a part of a taxpayer's building or buildings or any part thereof;

  (6)  The term "taxable year" means the calendar year in which the tax is payable;

  (7)  The term "taxpayer" means any banking institution subject to any tax imposed by this law.