The term "net income", as used in this chapter, means taxable income as determined for a regular corporation in Chapter 6 of this title after deducting all earnings accrued, paid, credited, or set aside for the benefit of holders of savings or investment accounts, any additions to reserves which are required by law, regulation, or direction of appropriate supervisory agencies, and a bad debt deduction. The bad debt deduction allowable for South Carolina income tax purposes is the amount determined under the Internal Revenue Code as defined in § 12-6-40. No deductions from income are allowed for any additions to undivided profits or surplus accounts other than herein required, and for the purposes of this chapter, a state-organized association is allowed the same deductions for bad debt reserves as those allowed to federally organized associations. Associations shall maintain the bad debt reserves allowed as a deduction pursuant to this section in accordance with the provisions of the Internal Revenue Code as defined in § 12-6-40 and shall keep a permanent record. These provisions are controlling notwithstanding any other provision of law.