999999: Error executing function. The value being added to the CodedValueDomain already exists

Error Message

In some instances, when using the Table to Domain geoprocessing tool the tool fails to run and the following message is displayed:

Error:
99999: Error executing function.
The value being added to the CodedValueDomain already exists.

Cause

The error occurs if a duplicate code value in the table is used as an input in the tool.

Solution or Workaround

1. Navigate to Arc Toolbox > General and run the Delete Identical tool.
2. In the Input Dataset, click the Browse button and select the table.
3. Check the Field(s) to be checked for duplicates.
4. Click OK.