Cst sales by urd dealers or under application dealers

Dear Sir

I have a client who is currently under application for Mahavat / CST in Mumbai. They are importers and have received there first consignment . They need to issue a local sales invoice for inter state sale. As they are still under process of registration , how can they issue a interstate CST / TIN invoice ?? please guide , if any undertaking forms are avialable under which it can be doen??

Regards

Sudhir