The Vehicle Identification Number (VIN) is required by an MOT station when the time is due for your Roadster's annual checkup. However, if you take the car to an MOT station that isn't familiar with smarts, they may struggle to locate the VIN and ask you. For your information, the VIN in the Roadster is located in two places.
The first place to check is the driver side door jamb.

The VIN on all Roadsters starts with 'WME452...'. However, if the VIN plate is missing from the door jamb, there is a second, more permanent place you can check.

Open the boot, remove the carpet and the engine cover. The VIN is etched into the Tridion seam at the back of the engine bay.