Fly-tipping is defined as the 'illegal deposit of any waste onto land that does not have a licence to accept it'. Tipping a mattress, electrical items or a bin bag full of rubbish in the street causes a local nuisance and makes an area look ugly and run down. This statement is from keep Britain tidy.
The Local Authority ultimately decides the difference between a littering offence and fly tipping, experience tells us usually one bin bag and above is considered so. The legislation explains the law and the rules around illegally depositing waste.