Bizum

...is the immediate payment system via mobile phones/ mobile banking, here in Spain. The current limit anyone can send is €5000 a month, with a maximum of €500 in one transfer. In June this will change to a maximum of 30 payments a month each payment between 50c up to €500.

All you need is a friend's phone number, and know that they also use bizum to be able to send them money. It is so convenient IMO.

However if you're getting payments through bizum for goods or services they have to be declared to the Hacienda as part of the yearly tax declaration.