1. Every credit institution as herein defined shall be subject to an annual tax for the privilege of exercising its franchise within the state of Missouri, according to and measured by its net income for the preceding calendar year.
2. The rate of tax for each taxable year shall be seven percent of such net income.
3. Each taxpayer shall be entitled to credits against the tax imposed by sections 148.120 to 148.230 for all taxes paid to the state of Missouri or any political subdivision thereof during the relevant income period, other than taxes on real estate, contributions paid pursuant to the unemployment compensation tax law of Missouri and taxes imposed by said sections.