Eco receipt / Receipt

Nowadays, whenever people buy something, they always get receipt. Receipt is something that useful for keep account, and for government's tax management. But, what is the material of receipt?
It's paper. Everybody using it everyday, but rare did people realize that it's a waste of natural resources. If all the people using electronic receipt, than it will be save lots lots of paper. The amount will be astonishing!
The Eco Receipt i designed, have 3 function. First, of course, it's an electronic receipt. 2nd, it also can keep your account, help you to well mange your spending & saving. 3rd. It has a function of calculator for temporary use.