User tries to delete an existing Withholding Tax Code but encounters the error above.
The Available On field is a mandatory field in the Withholding Tax Code form but it does not have any value populated and the field is greyed out.
Solution
User can manipulate the form using the Console window by doing the following:
Navigate to Setup > Withholding Tax > Tax Codes
Withholding Tax Code: Click Edit
Press fn + F12
Console window: Enter nlapiSetFieldMandatory(‘custrecord_4601_wtc_availableon’,false)
Press Enter
Click Delete