Expats selling NGO cars haven't paid tax, the new buyer is responsible for this and in addition to the high expense (taxes range from 40 to 180%, sometimes based on the original value of the car) and it is an increasingly difficult process to go through.
Also, driving with a car for which the tax is unpaid is risky: the car may be impounded until the tax is paid and all the necessary paperwork has been done, which can take weeks (There are several hundred cars sitting at the Lao-Thai Friendship bridge for which the owners won't even bother going through the process of getting them back - go see for yourself!)
source for posting below: http://www.expat-advisory.com/articles/southeast-asia/laos/buying-car-and-number-plates-laos
Buying a car and number plates in Laos
By: Thomas Wanhoff Posted: January-02-2011 in
* Laos
* Expat Life
When you arrive as an expat in Laos, the first thing you want to have is transportation. Beside the golfcarts, which are actually public buses, there is no public transportation in Laos, and Tuktuks are too expensive for a daily commute.
So you want to buy a car. You may find some advertisements at Phimphone or Simuang supermarket. Due to high tax cars are expensive, even if they are 12 years old, so expect to pay from US$3,000 up.
Most important is that the tax is paid. This is usually not the case if the car belongs to a diplomat or NGO employee. You should ONLY buy a car where the tax is paid already (if not, expect to pay tax for the last X years; that can be some thousand dollars). But how do you know if the car belongs to a diplomat or NGO employee? The number plate.
If the number plate is white with blue letters, it is an NGO or diplomat car and usually has not had tax paid. If the number starts with 'N2', then tax definitely hasn't been paid.
If the car is registered to a company, it will have a white number plate with black letters. If it is registered to a foreigner, it will have blue letters on a yellow background. While black letters on a yellow plate are reserved for Lao nationals.
The car documents should include an ownership card (it is a plastic card, like a credit card) and the yellow book. You also should ask if it is insured. If it is not, Toko gives you a good service in Laos.
Once you have made the deal, you need to register the car in your name. This is not easy, and I don't recommend you do this on your own if you are not fluent in the Lao language. Use a service like J&C. They did a great job for me, and my case was really complicated .
