Which DVLA postcode to use?
While the DVLA is based entirely in Swansea, they do have a few different postcodes to use for different forms and processes. For example the main one is SA99 1AR which is used for V890 and V11 forms. You can also use SA99 1BA for V5 changes.
If you have vehicle or driver record enquiries such as to see is someone has a valid license, then send it to SA99 1BN while driving license renewals are sent to SA99 1DH. The personalised registration plate department is at SA99 1DS while enforcement related paperwork and queries should be sent to SA99 1AH.