Small slips of paper you normally receive at the shops as proof of purchase
The majority will need to be placed in the general waste bin
Most of the receipts we are issued with are printed on thermal paper [they print in seconds] which is constructed of more than one layer and has been treated with chemicals, this paper will have a sheen to it and feel smooth.
The only exception is where you are given a receipt on paper which is more like newsprint and will have ink on it, this receipt will normally take longer to print and the paper will not be shiny and is normally rough to the touch.
Where possible ask for no receipt and give an email address instead, this will also ensure that you don’t misplace the receipt if an item ever needs to be returned