This Part provides for due dates of payment and the collection and recovery of corporation tax or an overpayment of a tax credit under Part 16. Tax paid late shall carry an additional charge and compensation is payable on refunds made by the Tax Department. The rate of such charge or compensation, as applicable, will be set at a commercial rate and is not penal. The additional charge levied on tax paid late is not an allowable tax deduction, and compensation received on refunds is not taxable.