Police in Hanoi have begun to penalize vehicle owners who have not transferred ownership from the previous owner, but a top police official said the new regulation is difficult to enforce.
Major General Nguyen Van Tuyen, director of the Road and Railway Traffic Police Department, admitted that there is no way for officers to know if a vehicle has been bought without transfer of ownership or just borrowed.
"The Ministry of Public Security will study and find a solution for this," the government website quoted him as saying.
It is common in Vietnam for vehicle sellers and buyers not to register the sale of a vehicle to evade taxes.
Tuyen said the government lost tax revenues as a result.
In September the government issued Decree 71/2012 superseding a 2010 decree on traffic violations.
It prescribes a fine of VND800,000-VND1 million (US$38-48) if a new owner of a motorbike has not obtained the title to the vehicle. For automobiles it is VND6-10 million.
As of September Vietnam had more than 35.6 million motorbikes and 1.97 million automobiles.