Here is some useful info for vehicles from a local site.
CROSSING AZERBAIJAN WITH YOUR OWN VEHICLE
There are 2 ways to cross Azerbaijan territory with your own vehicle. It is either to transit Azerbaijan or apply for temporary entry (up to 30 days).
Temporary entry (up to 30 days)
At the link below you can find regulations on foreign registered vehicles entry to Azerbaijan.
Unfortunately that information is in Russian, we will quote below just some extras in English which we believe might be helpful to independent travellers.
3. Временный ввоз транспортных средств на таможенную территорию Азербайджанской Республики физическими лицами
3. Temporary entry of transport vehicles to the territory of Azerbaijan by individual persons.
3.1. Транспортные средства всех видов, взятые на постоянный учет в иностранных государствах, декларируются физическими лицами в таможенном органе, действующем в пограничном пропускном пункте, в отношении них осуществляется таможенный контроль, у лица, перемещающего транспортное средство, берется обязательство об обратном вывозе транспортного средства и выдается разрешение на его временный ввоз на таможенную территорию Азербайджанской Республики.
3.1. Transport vehicle of any type registered in other country have to be declared by individual person at Customs station operating at border point. Obligation to leave with vehicle Azerbaijan is taken from individual and permission is given for temporary entry to Azerbaijan territory.
3.2. В случае если транспортные средства, временно ввозимые в Азербайджанскую Республику на срок до 30 (тридцати) дней и относящиеся к товарной группе 8703 ТН ВЭД, ввозятся непосредственно физическими лицами-нерезидентами, транспортное средство оформляется таможенным органом, действующим в пограничном пропускном пункте, без внесения денежных средств на депозитный счет и принятием от лица, перемещающего транспортное средство, обязательства об обратном вывозе транспортного средства.
3.2. If transport vehicle entering Azerbaijan territory for a period of up to 30 days is listed in '8703 ТН ВЭД' and is taken by an individual person who is non-resident of Azerbaijan then official documents are issued by Customs station operating at border point without taking money deposit and but just obligation that vehicle will leave Azerbaijan territory within 30 day period.
Here is link to LP Forum with comments of the driver that crissed AZ in his own vehicle: Travelling to Azerbaijan with a Foreign Car - My Experience - Lonely Planet travel forum
Entering Azerbaijan through the Lagodekhi- Belakan border crossing (Mazim Çay):
I got a 30 days permit for the car. I had to pay 15USD road tax and 5USD (actually it is 2,5AZN but they charge 5USD) for an insurance (third party liability of course). You must pay in USD. The insurance covered up to 1000AZN of property damage and up to 5000AZN of body harm. Azerbaijan was the only country of the Caucasus which had an (compulsory)insurance available at the border. I also had a secondary cover third party liability insurance with Ingosur (up to 1.000.000USD).
Azeri law allows you to enter for up to 30days without leaving a deposit(don't do this, because there is no bank to get your money back at the border) with a foreign-registered car IF:
Your car is owned by yourself. (no leasing).
It is a car (not a motorbike).
It is a left-hand drive (no hand-drive cars are allowed in the country (like most UK cars)). (Which, BTW is illegal because it violates the provisions of the Vienna/Geneva Road Traffic Conventions, of which Azerbaijan is a signatory country).
It has normal registration plates (no transit ones).
All this is written on the web site of the Azeri customs (in Azeri and Russian only, of course
They were very friendly on the border crossing. It took about 2 hours both sides. There were 3 more cars. I got about 6 or 7 different and very beautiful papers on the Azeri part.
Source: LP Forum, qwer1234
Transit is allowed for 72 hours only. Customs declaration and obligation to leave with vehicle the territory of Azerbaijan will be taken from you. Unless you leave a full-value cash deposit back at the border (which will be returned to you when you exit), you may only keep the car in for 72 hours since you enter Azerbaijan. $15 road tax have to be paid. Otherwise, for periods exceeding 72 hours a several thousands deposit for the car has to be paid, and you must use the same entry and exit points to get the deposit back. For example, for the motorbike the deposit is around $3500 USD. They don't accept credit cards obviously.
We can also recommend you to check Forum Azerbaijan - Lonely Planet travel forum
where you can find some useful information.
Read a post here.
Right hand drive vehicles in Azerbaijan
Right hand drive vehicles are illegal in Azerbaijan and officially are not allowed to enter. Official Regulations (only in Russian) are available here:
8.1. Ввоз в Азербайджанскую Республику транспортных средств с рулем на правой стороне запрещается.
8.1. RHD vehicles are not allowed to enter the territory of Azerbaijan Republic.
Transit is not an option for RHD, which are not even allowed to enter Azerbaijan territory according to regulations.
Despite the fact that officially RHD vehicles are banned in Azerbaijan most (if not all) tourists manage to cross Azerbaijan without any hassle.
At the link below you can learn about experience of other people non-residents of Azerbaijan who tried to cross Azeri territory with RHD vehicles. Right hand drive vehicles in Azerbaijan. - Lonely Planet travel forum
Azerbaijan with a RHD car - Lonely Planet travel forum
Hope this info is useful