Rare business term for goods on hand or stock. More commonly expressed as 在庫 (zaiko).
See also: 在庫
We check the stock every day.
Alternate kanji spelling using 在, which reinforces the 'existing' nuance.
Compound of あり (ari, 'existing') + 荷 (ni, 'cargo, goods'), literally 'existing goods'. The exact historical derivation is uncertain, but it follows a common pattern for business terminology.