AR meaning in International ?

Avis de réception (English: advice or acknowledgment of receipt) is a postal service returning to the sender a form or card signed by the recipient. This is evidence that the letter was received, and these forms (or cards) are frequently seen with legal endorsements. It had existed under various names in some postal entities as early as the late 18th century, and was adopted by the GPU General Postal Union in 1875, and again by its successor, the UPU Universal Postal Union in 1879.

Equivalent terms include aviso de recibo, acknowledgment of receipt (Canada), advice of receipt, advice of delivery (UK and much of the Commonwealth), return receipt requested/required/wanted/demanded (US), Zustellungsurkunde (Germany), ricevuta di ritorno (Italy), zwrotne potwierdzenie odbioru (Poland), aviso de recepción (Salvador 1897 stamps), and many others. The term accusé de réception is sometimes seen, although it is inaccurate. The standard abbreviations are AR and AD.