Letter precedent to listing requires Authority approval before securities issuance or listing applications proceed. A mandatory pre listing clearance requires an applicant to obtain a letter precedent to listing from the Authority before issuing securities proposed for listing or before submitting a listing application; applicants also must obtain an in principle approval from the exchange prior to issuing any class of securities, exchanges must not consider listing applications unless accompanied by the Authority's letter precedent, and the Board with the Authority may exempt these requirements for specified securities or periods on stated conditions.