If you've lost your parking permit in Braintree, you should report it to the North Essex Parking Partnership. Unfortunately, the council's documents don't specify the exact steps for reporting a lost or stolen permit, but generally, it would involve contacting them directly for assistance.
You can reach the North Essex Parking Partnership at 01206 282316 for more detailed guidance on how to proceed. It's a good idea to report the loss as soon as possible to prevent any unauthorized use of your permit.