# Stock items

A stock item keeps the inventory of an [SKU](https://docs.commercelayer.io/core-api-reference/skus) in a given [stock location](https://docs.commercelayer.io/core-api-reference/stock_locations).

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The actual availability of an item may vary depending on active [stock reservations](https://docs.commercelayer.io/core-api-reference/stock_reservations). If active stock reservations are associated with a stock item, the *available* quantity equals the stock item quantity minus the [reserved stock](https://docs.commercelayer.io/core-api-reference/reserved_stocks) quantity.
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When you place an [order](https://docs.commercelayer.io/core-api-reference/orders) the related stock is reserved. As soon as the order is approved the related stock is released and the stock item quantities get decremented. When a [return](https://docs.commercelayer.io/core-api-reference/returns) is approved and the associated items are restocked, the stock item quantities get incremented.

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When updating stock items quantities via [imports](https://app.gitbook.com/s/-LgByaSP8eKjad-MIuHE/importing-resources), existing records may be updated inconsistently: this occurs when the quantity of a stock item is less than the existing reserved stock, which is probably an overselling symptom. To avoid this scenario, we recommend passing the `_validate` trigger attribute for each of the imported inputs, as shown in [this example](https://app.gitbook.com/s/-LgByaSP8eKjad-MIuHE/importing-resources#importing-a-list-of-stock-items-csv).
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