what is the jist with chassis numbers when buying a ready made chassis

im looking at purchase of a mk indy
is the chassis number already done or is it up to the owner to sort that sort of stuff out?

I bought an avon chassis and body and with it got a vin plate with the chassis no on it and the body colour code

We bought a Luego chassis and there is no chassis number on it. I think you will probably find the same is true of MK chassis. There is a post elsewhere that discusses how to get a chassis number.