If you've completely used up the balance on your voucher, you won't have to worry about anything. In the event where there is no more money left on the card, the PIN will become useless. On the other hand, you can use the same voucher to complete several payments with it until the finances on it are depleted. If that's the case, remember to always safeguard the details of your eVoucher regardless of how much money you have left in it.