For every friend who becomes a UNDO customer via your link, you will receive a €4 discount per month for 12 months. The person you refer will also receive a €2 discount per month for a whole year. These amounts are automatically deducted as a discount on your monthly invoice. The first discount will be applied to the invoice for the month following the one in which your friend joins UNDO. Have you invited several friends and built up more discount than your monthly amount? Then you simply pay €0.