My summary says that my tax refund was applied on unpaid taxes. What does this mean?

Your summary not only contains a list of your overdue taxes; it can also inform you that an unpaid tax has become covered by an amount that would otherwise have been refunded to you. In general, starting on the date when your tax assessment is completed, the Tax Administration uses refund money on any unpaid taxes for which the due date is the 4^th of the next month (if you are an individual taxpayer) or for which the due date is the 18^th of the next month (if you are a corporate taxpayer). If the due date has already passed, the Tax Administration covers the tax debts with your refund immediately on the end date of tax assessment. If the due date has not arrived yet, the Tax Administration will wait until the due date before covering taxes with a refund.

You can also see your tax summary in MyTax.