Instalment payment of tax permitted subject to commissioner approval, interest and prescribed conditions; default accelerates recovery. The Commissioner may, for reasons recorded in writing, allow a taxable person to extend time for payment or to pay amounts due (excluding self-assessed liabilities in returns) by monthly instalments not exceeding twenty-four, subject to interest under section 50 and prescribed conditions; default of any one instalment makes the entire outstanding balance immediately payable and liable for recovery without further notice.