If you have mistakenly added an additional line of information but have not completed the required information, this message can display when attempting to leave the Case page on your New Case Draft.
A common scenario is if you click the +Add Case Cross Reference Number button (specific to Cook County, Illinois filers), after already completing the field (screenshot as an example). Doing so creates an extra line of data that is not needed. You would need to remove the duplicate line that has no data to be able to proceed.
Failing to complete this section or any required data in general on the Case Information page will also contribute to this error: