Postal codes in Azerbaijan consist of four digits.
The four-digit postcode indicates the nationwide format AZ NNNN. The first two digits indicate the regions of Azerbaijan in accordance with the modern administrative divisions, including the Nakhchivan Autonomous Republic and Nagorno-Karabakh.
From 1970 until 1991, when Azerbaijan was part of the Soviet Union as the Azerbaijan SSR, the entire territory of the Soviet Union used the six-digit postcode 37NNNN. After gaining independence, Azerbaijan switched to the current four-digit postcode.