Vouchers were a resource obtainable in-game that could be substituted for Balens in some situations.
As of patch 2.1, Vouchers were removed from the game and changed to Bound Balens at a rate of 20:1. Bound Balens will work the same way as regular Balens except some payments (for example, Hot Items in Shop).
Where Vouchers used to be awarded, other items have been substituted. But mostly, the rewards are Bound Balens in quantities of two to four. The exception is the Tree of Ancients on a player's farm. The tree now awards Daru instead of Vouchers.