Transaction &1 cannot be deleted

What causes this issue?

You want to delete planning data in fiscal year &V2& in plan version
&V3&. Deletion is not possible for transaction &V1&. The corresponding
data that was created automatically needs to be reversed first. For
more details, see note no. 520890.

System Response

The system ignores the transaction, but all other data can be deleted.

How to fix this error?

If you want to delete the data of this transaction, reverse it first
using the appropriate transaction.

Error message extract from SAP system. Copyright SAP SE.