Chancellor Alistair Darling announced that VED refunds would be restricted to registered keepers.
It would apply only when vehicles have been stolen, destroyed, sold/disposed of, declared off-the-road, or exported.
The finance director of a large dealer group said: “This would appear, on the surface, to have a considerable impact on one of our revenue streams.”
He said the DVLA website provided no additional information.
Accountants who have contacted the DVLA were told no information was available.
A Treasury spokesman said the new rules would apply from January 1 next year.
“The aim is to prevent owners of vehicles from cashing in existing VEDs ahead of the introduction of a higher rate, and buying a new one at the existing, lower rate.”
He said the intention was not to penalise dealers.
Deloitte tax specialist Steve Holloway said: “This is an extremely complex area which we are still looking into.
“It appears that the Treasury may have a different set of rules for dealers, who may not be prevented from claiming VED refunds, but this is still not clear.”