How to block the employees from requesting an advance if they have unreported advances?

You can set up a custom approval flow in such a way that it automatically rejects the submitted advance if there are unapplied advances for the employee. To do this:

• Go to Settings on the left sidebar.
  (OR)
  Click Settings in the top right corner of the page.
• Navigate to Module Settings.
• Select Advances under Travel & Expense.
• Go to the Approvals tab.
• Click Custom Approval.
• Click + New Custom Approval.
• Enter the Approval Name and Description for the approval flow.
• Configure the criteria as “When - Has unreported advance - is - True” in the Define the criteria (if any) section.
• In the Approvals section, select Auto Reject.
• Click Save.