How To Fix VFKK121 - Billing type of reversal &1 or original &2 not of type invoicing order

SAP Error Message - Details

• Message type: E = Error

• Message class: VFKK -

• Message number: 121

• Message text: Billing type of reversal &1 or original &2 not of type invoicing order

What causes this issue?

The billing type &V2& and the assigned reversal billing type &V1& have
to be treated the same by FI-CA invoicing. That means that they both
have to be processed with an FI-CA invoicing order, or they both have to
be posted directly as FI-CA documents.

How to fix this error?

Change the settings in posting area 1205 in Customizing for Contract
Accounts Receivable and Payable under <LS>Integration -> Sales and
Distribution -> Define Settings for Transfer to Invoicing</>.

Error message extract from SAP system. Copyright SAP SE.