Message type: E = Error
Message class:  FMCA_INV_GTR - Grantor Billing: FICA Invoicing 
Message number: 020
Message text: Enter Grantor object type, Grantor object ID and Logical System
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.
Unfortunately, there isn't any extra information in this error notice.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message FMCA_INV_GTR020 typically occurs in the context of the Funds Management (FM) module when there is an issue related to the grantor object in a financial transaction. This error indicates that the system requires specific information about the grantor object type, grantor object ID, and logical system, which are necessary for processing the transaction correctly.
Cause: Missing Information: The error usually arises when the required fields for the grantor object type, grantor object ID, or logical system are not filled in or are incorrectly specified.
Configuration Issues: There may be configuration issues in the Funds Management settings that prevent the system from recognizing the grantor object. Data Inconsistencies: There could be inconsistencies or missing entries in the master data related to the grantor object.
Solution: Check Input Fields: Ensure that you have entered the grantor object type, grantor object ID, and logical system correctly in the relevant transaction. These fields must be filled
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
FMCA_INV_GTR016 A reversal billing document cannot be reversed
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCA_INV_GTR015 Grantor item object identifier & is missing
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCA_INV_GTR021 Enter Logical system because entered Agreement ID, Claim ID is not unique
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCA_INV_GTR030 Grantor billing documents exist for PSCD. Action not possible
What causes this issue?  You tried to delete/change the default Financial Execution Interface (FEI) entry, but there are Grantor billing documents for...
Click on this link to search all SAP messages.