Methods and apparatus, including computer program products, for payment card terminals for mobile phones. In general, data characterizing a payment card and a settlement amount for a transaction may be received, where the data is user-generated input and is received at a mobile phone associated with a mobile phone number. Wireless transmission of data characterizing a request to provide a payment card settlement service of a merchant account of a merchant account provider for the transaction may be initiated, where the wireless transmission is to be from the mobile phone over a carrier data network to an application server. Data characterizing authorization of settlement of the transaction with the payment card may be wirelessly received by the mobile phone from the application server.