Cheers @jojo22
If I remember correctly, I received this certificate along with my first PIP award in 2013. I used it to tax my existing private car without cost. When I joined the Motability scheme in 2014 I part-ex’d my private car and then had automatic free tax as part of my Motability package. I inherited an old car in 2021 and needed this certificate then to apply my tax exemption to this inherited car. My Motability car then was an EV so there was no car tax liability so I just notified Motability I wanted to be personally liable for the EV at zero tax freeing up my exemption for use on the other vehicle. As far as I’m aware, the Certificate of Entitlement’s only purpose is to evidence entitlement to car tax exemption on a single vehicle.
Anyone who is on the scheme with a single vehicle would never have had any use for this certificate. I don’t know if things have changed since 2021 and other proofs are now acceptable. Then the Post Office would not apply the exemption without its production.