Message type: E = Error
Message class:  GTR_FI - Grantor Fi Integration 
Message number: 148
Message text: Select a GM-GTR billing document first
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The SAP error message GTR_FI148: Select a GM-GTR billing document first typically occurs in the context of the SAP Global Trade Services (GTS) module, particularly when dealing with billing documents related to Global Trade Management (GTM) and GTR (Global Trade Regulation).
Cause: This error message indicates that the system expects you to select a billing document related to Global Trade Regulation (GTR) before proceeding with the transaction. The error can occur due to several reasons: No Billing Document Selected: You may not have selected a billing document in the transaction where this error appears. Incorrect Document Type: The document you are trying to process may not be a valid GTR billing document. Authorization Issues: There may be authorization issues preventing you from accessing the required billing document.
Configuration Issues: There could be configuration settings in GTS that are not set up correctly, leading to this error.
Solution: To resolve the error, you can take the following steps: Select a
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