You may be required to provide a security deposit when registering for GST if at least one of the directors or partners of the business:
Security deposit may also be imposed for any other reasons that the Comptroller deems fit. We will notify you on the amount of security deposit required upon processing your application for GST registration. The security deposit must be in the form of a banker's guarantee or insurance bond. We may waive the requirement of the security deposit if the outstanding issues with us are settled.
A possible reason is that at least one of the other directors or partners of your business:
However, due to official secrecy laws, we are unable to inform you of the details like identity of person owing the tax, nature and quantum of the outstanding tax/penalties owed to us.