There are new rules for applying for Vehicle Excise Duty (VED) for road engines including ploughing engines. These came into force in May 2018.
To obtain VED at the zero rate ploughing engine (and other traction engine) keepers will have to apply for an exemption via DVLA form V112G and quoting Category 26.
There has been a great deal of confusion on this matter and advice you may have seen from elsewhere may have been incorrect. There is no general exemption for road steam as reported previously.
SPC will continue to argue that the only sensible way forward is a general exemption for steam despite representations to government. SPC members may well question why they have to seek an exemption for a test that doesn’t exist for ploughing engines. It is not sensible.
To use an untaxed vehicle (even at the zero rate) can have implications for road insurance and may draw engines on the road to the attention of the constabulary.