GNU Taler (Taxable Anonymous Libre Electronic Resources) is a new secure electronic payment system based on open standards, free software, and advanced cryptography. GNU Taler provides privacy guarantees to the buyer while offering the possibility to audit merchants, making sale incomes transparent and fraud difficult. To online merchants and retailers, GNU Taler offers instant transaction clearance without risks of fake payment methods. Computations needed to clear the payments are efficient and scalable so that banks can pass on lower transaction costs to consumers and merchants.