Message type: E = Error
Message class:  FKK_ID_PT_SIGN - Digital Signature Portugal FI-CA/IS 
Message number: 318
Message text: Interval/Series Check failed
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The SAP error message FKK_ID_PT_SIGN318 indicates that there is an issue with the interval or series check in the context of contract accounts receivable and payable (FI-CA). This error typically arises when there is a problem with the data consistency in the billing or payment processing, particularly related to the intervals defined for a specific contract or account.
Cause: Incorrect Interval Definition: The intervals defined for a billing document or payment may not align with the expected values in the system. Data Inconsistency: There may be inconsistencies in the data related to the billing or payment documents, such as overlapping intervals or missing entries.
Configuration Issues: The configuration settings for the billing or payment processing may not be set up correctly, leading to validation failures. Missing or Incorrect Master Data: The master data related to the customer or contract account may be incomplete or incorrect.
Solution: Check Interval Definitions: Review the interval definitions in the relevant billing
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