Here's the description a text provided by SAP gives of what a delta accrual is:
"This settlement type can be used to make corrections to accruals that are required because the condition data has changed. It does not matter whether the accruals already existed when the service was provided. Existing accruals are automatically cleared."
In the case of the standard condition contract 0S12, the customer settlement document type assigned for delta accruals is 0S42. In turn, this document was assigned the document schema group 0T. Finally, you have the following pricing procedure determination for the documents with this document schema group:
If you check pricing procedure A10006, you get this:
My question is: how can the system correct formerly posted accruals if no account key is defined for any of the price conditions in pricing procedure A10006 on the accrual account key column (the last column in the figure above)?