Morning, Mr. You have to surrender your plates before you end the vehicle's liability insurance coverage, or when you will not use the registration.
I have a trailer, and my plate got stolen on a trip to the beach. I found out yesterday I had no plate, what should I do?
Don't worry,  as you may already know: "normally" a trailer does not need liability insurance, so DMV will not suspend your driver license or registration because your plate got stolen, and therefore you will fail to surrender it.
So, just to make sure: do I need yo surrender trailer plates?