SAP Note 16176 - Posting manual, special depreciation + automatic normal depr

Symptom:

A special, manual depreciation to the tax area should be posted with movement type 642.
With the entry of the depreciation value, error message 649 is displayed which states that in the calculatory area, only a negative depreciation value can be posted.
In customizing, the depreciation areas are controlled in such manner that they are inde-pendent of each other up to the acquisition value. How can the manual, special depreciation be posted, without the calculatory or book depreciation area being taken into consideration (Change to Customizing necessary)?

Cause and prerequisites

The manual, special depreciation are posted in only one area (e.g., 15 Taxation Law), and in no other area.

Solution
Define your own depreciation key (it must be a copy of 'MANU' key). In this depreciation key, enter the desired calculation key for Normal depreciation; it may have only the acquisition costs and cost of goods manufactured as a base value. In the special deprec. line of the deprec.key, your own calculation key must be entered which manually calculates the special deprection. For this process, calculation key 3010 can be copied, for example. The only change is the depreciation type, from 'N' to 'S'. For posting manual special depreciation, movement types 620 and 630 are to be copied and the area in question is to be entered in the area selection for movement types. This area is to be posted with BWA. The posting is carried out via -Post-Other (transaction AB01).