Export bond or Letter of Undertaking for GST requires security, renewal, and tax payment with interest on default. Form GST RFD-11 prescribes a bond or Letter of Undertaking to secure export of goods or services without payment of integrated tax, requiring bank guarantee details, renewal obligations, departmental power to invoke guarantees, and an obligation that tax and lawful charges be paid within fifteen days of written demand; the LUT additionally imposes an eighteen percent per annum interest charge on tax payable if export obligations are not met.