I try to understand how it is possible to manage on an accounting point of view the materials that are issued to a cost center and then restocked. Then they are issued to another cost center (as second hand) etc...
For that kind of materials, not consumable, but also not only used one time by one cost center, the policy of valuation is something quite complex. How should this be managed?
There are a few options available in situations where inventory items are used internally and then put back into inventory. A key question to address first is whether or not the value of the item is impaired by its temporary use.
If the value is not affected by temporary use, then the item could be "consigned" to the cost center. In this case, the dollars would stay in inventory, but there would be an audit trail in SAP indicating the item was not physically sitting in the warehouse.
Let's say the value is impaired by temporary use. The simplest option would be to charge the cost center with the full dollar value of the item, and then bring it back at, say, a value of one penny. Perhaps not even put the item back on the books at all, but instead store it in a clearly marked "supplies" area in the warehouse. Then, the next user would get it for "free".
Things get quite complicated as we try to apportion value to different internal users. One possible scheme would involve creating a series of "R" part numbers to indicate the item was "Returned" as opposed to new. The "R" parts would be valued at some fraction of the "new" cost - that would be a management call. Then, the department would get charged the "new" (higher) cost when the part was issued, and credited at the "R" (lower) value when they returned it. The department's cost report would then reflect the difference between these values as a consumption expense. Of course, this can lead to a vicious downward spiral of "R", "RR", "RRR", (etc.) part numbers and associated values if a true obsession develops with apportioning costs in this manner.
Because of the complexity that can quickly develop, a cost/benefit analysis should be done before launching into any apportionment scheme. The key question becomes "Is there a clear business need for this information that would justify the costs involved in obtaining it?" The key question can be re-phrased "Do my customers see value in my company knowing this information?" If the answer is a heartfelt yes, then proceed. But less intense cost strategies often rise to the surface under the harsh light of scrutiny.