How to add or remove a voucher expiry date
Select the Vouchers module.
Select List Vouchers.
Click edit on the voucher you would like to change.
Click the Restrictions tab.
Click Hide expiry date on voucher.
Click save changes.
Note: If the Hide expiry date on voucher flag is already ticked and you want the expiry to show on the voucher, untick the flag so it shows.