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Fix/remove the payroll categories in Workbench and re-export.
Note: this could be an issue with caching, where Payroll Categories in MYOB got renamed or recreated, but the old IDs are still cached in Workbench. So if the error persists, delete the Financial Company’s setting value for the "MYOB Payroll Categories" Setting. This will cause the setting value to be repopulated with up to date Payroll Category IDs the next time the client export does an export.