From a family's Transactions tab, click View Unapplied Credits & Unpaid Fees to display a listing of all amounts. You can use the links in this report to make any necessary linking adjustments.
To find ALL families with unapplied credits and unpaid fees use the Search report from the Transactions menu with a wide date range and the Special Search criteria All unpaid credits and unpaid fees selected.
For more information check out the Locate and Correct Unlinked Fees section of Help articles.