Note the application of credit 1026894 on the 15th
A credit was applied to invoice 10259336 the 15th of the month.
The most comprehensive method of reporting the application of credit is found within Reports > AR > Applied Credits report.
In the example, the From Date has been changed to the beginning of the year and the Customer ID, 894, has been entered to filter the report.
The resulting report presents the application of credit 1026894 to two invoices on 1/15. Invoice 1059336 is included in this distribution.
Answer: A prior credit was applied to invoice 1059336 on 1/15.
If this distribution is incorrect, the AR > Reverse Credit App. will allow the user to remove the credit application which results reestablishing the credit balance. Use AR > Apply Credit to apply credit to the applicable invoices as desired.