Do not enter aux. acct assignment for G/L acct or fixed asset receivers

What causes this issue?

You want to settle a G/L account or fixed asset, and have entered
another account assignment (such as, to cost center).

System Response

If a source structure is stored in the settlement parameters, and there
is no settlement rule <ZH>with</> a source assignment for a debit
record, but there is a settlement rule <ZH>without</> a source
assignment, then the system chooses this settlement rule.

How to fix this error?

Delete the additional account assignment. If you want to distribute the
costs to be settled to different receivers, then you need to create
more than one rule.

Error message extract from SAP system. Copyright SAP SE.