Message type: E = Error
Message class:  CNV_DMC_SIN - Messages for s-innovations migration 
Message number: 157
Message text: Tax category cannot be initial in conversion rule &1
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The SAP error message CNV_DMC_SIN157 indicates that there is an issue with the tax category in a conversion rule during a data migration or conversion process. Specifically, the error states that the tax category cannot be initialized (i.e., it cannot be left blank or set to an invalid value) for the specified conversion rule.
Cause: Missing Tax Category: The conversion rule is trying to process data where the tax category is not defined or is set to an initial (blank) value. Incorrect Configuration: The tax category may not be properly configured in the system, leading to the inability to assign it during the conversion. Data Mapping Issues: There may be issues in the mapping of source data to the target system, where the tax category is not being correctly assigned.
Solution: Check Conversion Rules: Review the conversion rules in the Data Migration Cockpit or the relevant migration tool you are using. Ensure that all required fields,
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