Letter of Undertaking for zero-rated exports secures tax exemption conditional on timely export and payment obligations if conditions fail. Clarifies that exporters opting to make zero-rated supplies without payment of integrated tax must furnish FORM GST RFD-11 (bond or Letter of Undertaking) prior to export, remain bound to pay tax with interest if export conditions are unmet, and that eligibility for LUT, bond requirements, bank guarantee conditions, validity periods, manual submission procedures until the portal is available, and continuous review of bond sufficiency are governed by rule 96A and related GST provisions.