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.[2]
^In areas controlled by the unrecognized Nagorno-Karabakh Republic, the postal codes are technically out of use and there is no the delivery of mail conducted between Nagorno-Karabakh and the rest of Azerbaijan.