Message type: E = Error
Message class:  HRPSGB_HER - HR PS GB Higher Education Messages (USS, HESA etc) 
Message number: 503
Message text: Initial period &1/&2 must be processed by &3 before any later period.
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The SAP error message HRPSGB_HER503 indicates that there is a processing sequence issue in the Human Resources module, specifically related to the handling of payroll periods. The message states that the initial period (identified by &1 and &2) must be processed by a specific payroll run (identified by &3) before any later periods can be processed.
Cause: This error typically occurs when: Payroll Processing Order: The payroll for the initial period has not been completed or has been skipped. In SAP, payroll processing must be done in a sequential manner, meaning that you cannot process a later period without first processing the earlier one. Incomplete Payroll Runs: There may be incomplete or erroneous payroll runs for the initial period, which prevents the system from allowing further processing.
Configuration Issues: There could be configuration settings in the payroll schema or control records that are not set correctly, leading to this error.
Solution: To resolve this error, you can
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