Message type: E = Error
Message class:  RP - Error Messages for Infotype Module Pools 
Message number: 337
Message text: W/S type & not allowed for pay.cat & (from & to &)
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The SAP error message RP337 typically indicates an issue related to the payroll processing in the SAP HR module. Specifically, the message "W/S type & not allowed for pay.cat & (from & to &)" suggests that there is a problem with the work schedule type (W/S type) being used in conjunction with a specific pay category (pay.cat) for a given period (from & to).
Cause: Invalid Work Schedule Type: The work schedule type being referenced may not be valid for the specified pay category. This can happen if the configuration does not allow certain work schedule types to be used with specific pay categories.
Configuration Issues: There may be a configuration issue in the payroll settings or in the work schedule rules that restricts the combination of work schedule types and pay categories. Data Entry Errors: There could be errors in the employee master data or payroll data that lead to this conflict. Time Management
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