Posting Liability for Cash Advances

Good Day,

What is the criteria for posting liabilities for a cash advance?  The cash advance was applied to the expense report, the report was paid.  The cash advance has been reconciled but it is not being selected when executing the post liability function for processing expenses.  In addition, what should happen when a cash advance is returned or repaid because the trip was cancelled?  There is not an expense report to be paid but the cash advance was deposited into the employee's account.

Any clarification on this matter is greatly appreciated.