Is it true that the general terms & conditions of the banks prohibit the disclosure of online banking login details and TANs?

The assertion of a breach of the general terms & conditions (prohibition of disclosure of PIN and TAN to third parties) is not correct. The German Federal Cartel Office (Bundeskartellamt) made its position clear in February 2011. It deemed general terms & conditions of German banks, or their interpretation, which prohibits the use of payments with direct banking to violate cartel law and called upon the banks to enable non-discriminatory access for online payment systems that are independent of banks, such as Pay now (known at the time as Sofort Überweisung). The banks have agreed not to claim publicly that users of payment methods such as Pay now were in breach of the banks’ general terms & conditions.