In some examples, a reader system is provided for managing inventory items in an inventory system. The reader system may be configured to read tags associated with items stowed in an inventory holder. The inventory holder may be detachably coupled to a mobile drive unit. The mobile drive unit may move the inventory holder to a first position near an antenna of the reader system and the tags may begin to be read. While reading or at other times in the reading process, the mobile drive unit may move the inventory holder relative to the antenna. The identified tags may be compared to a manifest list of items expected to be stowed in the inventory holder.