Wikipedia
Paym is a mobile payment system provided by banks and building societies in the United Kingdom. Recipients are identified by their mobile phone number instead of bank details such as sort code and account number.
The service was developed by the Payments Council and participating banks and building societies, with Bank of Scotland, Barclays, Cumberland Building Society, Danske Bank, Halifax, HSBC, Lloyds Bank, Santander and TSB involved from the launch in April 2014. More than 9 out of 10 current accounts in the UK support Paym after Clydesdale Bank, First Direct, Isle of Man Bank, NatWest, RBS International, The Royal Bank of Scotland, and Yorkshire Bank joined later in 2014. Nationwide Building Society joined Paym in June 2015, with Metro Bank and Tesco Bank planning to join later in 2015. The underlying network technology is provided by VocaLink, a member of the wider Single Euro Payments Area (SEPA) network. The name "Paym" is stylised in the logo with a slight gap between "Pay" and "m", and is a play on words over "Pay 'em", a contraction of "Pay them", and "Pay M" alluding to "Pay Mobile".
The recipient must register in order to link their mobile phone number with their bank account. Those wishing to make a payment to a registered phone number can use their existing mobile banking or online banking service. Payments made through Paym take place at the same speeds as existing Faster Payments or LINK payment mechanisms.
The sender enters the recipient's phone number (or selects their number in their own phone's address book). The sender's bank then retrieves the account number and sort code associated with that phone number, and then sends the money using the Faster Payments Service. The sender is shown the recipient's name (in order to confirm that they are paying the right person) but not their account details.