You may want to automatically reverse an accounting entry at a specific date.
This is, for example, used when you make a provision (e.g. provision for bad debt). When making the accounting entry for the provision, the amount you entered is only an estimated amount. You will only be sure of the amount at the end of the fiscal year. That's why, at that point, you want the accounting entry to be reversed to be able to enter the real loss that occurred.
For this, you just have to tick the box "Reverse Automatically" on the journal entry and to define a reversal date. The accounting entry will be reversed at that date.