I have an order from Benin, in West Africa. Buyer agreed to a 100 per cent TT payment, pls advice is it ok?

The buyer agreed to a 100 per cent TT payment, but he asked me to issue a revenue transfer monitoring authority (RTMA) centificate—as his country’s laws state that no importer can send the payment with out this certificate which shows that non-indgenious goods are imported.