How To Fix MN161 - Calculation rule &1 not defined (function module &2)

MN161 - Overview

• Message type: E = Error

• Message class: MN - Message class for subsequent settlement (Purchasing)

• Message number: 161

• Message text: Calculation rule &1 not defined (function module &2)

What causes this issue?

An evaluation of condition records with calculation rule &V1& is not
possible.
The program called for evaluation cannot process calculation rule &V1&.

System Response

The condition record is not evaluated.

How to fix this error?

Contact your system administrator, as an internal error has occurred.
The error occurred in function module &V2&.
Either this was called with incorrect data or evaluation of condition
records using calculation rule &V1& is not programmed.
The condition record concerned has (internal) number &V3&, and
condition item number &V4&.

Error message extract from SAP system. Copyright SAP SE.

MN161 - Details

• The SAP error message MN161, which states "Calculation rule &1 not defined (function module &2)," typically occurs in the context of the SAP system when there is an issue with the configuration of calculation rules in the system. This error is often related to the use of function modules that are expected to perform certain calculations but cannot find the necessary configuration or definitions.
  
  Cause:
  
  Missing Configuration: The calculation rule specified by &1 is not defined in the system. This could be due to a missing entry in the configuration tables.
  Incorrect Function Module: The function module specified by &2 may not be correctly implemented or may not exist in the system.
  Transport Issues: If the configuration was recently transported from another system, it may not have been transported correctly, leading to missing definitions.
  Custom Development: If there are custom developments involved, the custom function module may not be properly defined or activated.
  
  
  Solution:
  
  
  Check Configuration:
  
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