By law, carrier bags have added levies charged by retailers at point of supply.
Wales: Retailers must charge at least 5p for new single use carrier bags from 1st October 2011. Further information is here.
Northern Ireland: Retailers must charge at least 5p for new single use carrier bags from 8th April 2013. Further information is here.
Scotland: Retailers must charge at least 5p for new single use carrier bags from (20th October 2014 is the date in the draft Regulations). The draft document (approved overnight) is here.
England: In September 2013, the Government announced that it would introduce in England a levy of 5p on single-use plastic carrier bags in 2015. Small retailers with fewer than 250 employers will be exempt from the charge. The Government has also suggested that it may incentivise the use of biodegradable plastic bags, which might be exempt from the levy. The legislation is not yet available.