Message type: E = Error
Message class:  FKKBIX2 - Billing in Contract Accounts Receivable and Payable 
Message number: 171
Message text: Number for Posting Selected Items
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.
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The SAP error message FKKBIX2171, which states "Number for Posting Selected Items," typically occurs in the context of financial accounting, particularly when dealing with document postings in the SAP system. This error can arise due to various reasons, and understanding the cause and potential solutions is essential for resolving it.
Cause: Missing Number Range: The most common cause of this error is that the number range for the document type you are trying to post is not defined or is exhausted. Each document type in SAP has a specific number range assigned to it, and if this range is not properly configured, you will encounter this error. Authorization Issues: Sometimes, the user may not have the necessary authorizations to post documents, which can lead to this error.
Configuration Issues: Incorrect configuration in the financial accounting module or related settings can also lead to this error. Document Type Issues: The document type being used may not
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