You need to attach one of the following documents to demonstrate your authorization to display the registration number:

Vehicle registration certificate (V5C or V5CNI)
Green 'new keeper' slip from the V5C or V5CNI
Certificate of entitlement (V750 or V750NI) to the number
Retention document (V778)
Renewal reminder for vehicle tax or SORN (V11 or V11NI)
Temporary registration certificate (V379 or V379NI)
Number plate authorization certificate (V948) with an official stamp from the Driver and Vehicle Licensing Agency (DVLA)
Electronic number plate authorization certificate (eV948 or eV948/2)
Letter of authorization from a fleet operator (including lease or hire company) quoting the document reference number from the registration certificate
If your fleet is in the new V5C on demand scheme (also called 'V5C suppression'), a PDF of the vehicle's details from the view vehicle record service
UK trailer registration certificate (VTRC)

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