Reply from DVLA
Thank you for your email enquiry dated 21 May 2018, concerning a MOT exemption.
Under new legislation that came into effect on 20 May 2018, certain vehicles constructed or first registered more than 40 years ago are now exempt from MOT testing, unless they have been substantially changed.
As long as the DVLA have a date of manufacture/first use on the vehicle record which shows the vehicle is over 40 years old, the on-line tax renewal system should pick up that the vehicle is MOT exempt. I believe this action was taken when you taxed your vehicle. To make sure the exemption has gone through when you were taxing your vehicle I would advise you to contact the DVLA directly on 0300 790 6802.
I hope this information has assisted you with your enquiry, but if you have any further questions please do not hesitate to contact us again.