Costs already posted under cost element &. No deletion possible

What causes this issue?

You want to delete business process or cost center/activity type &V4&.
However, you have already posted actual costs in version &V3& in fiscal
year &V2& under cost element &V1&.

System Response

The deletion may therefore not be executed.

How to fix this error?

First reverse the posted record under cost element &V1&.
Alternatively you can set all fields to zero in the plan record you
have just selected. This corresponds to a deletion of the activity
types/business process quantity planning on object &V4&.
If the message appears several times in the error log, it could be that
the actual records were posted under different transaction currencies.
In this case, you must delete them all.

Error message extract from SAP system. Copyright SAP SE.