8 April 2013 Last updated at 17:03 BST
From today people in Northern Ireland will now have to pay 5p every time they need a plastic bag.
The money will be used by the government there to fund projects to help the environment.
Wales began charging shoppers for plastic bags two years ago, and it's expected to come into place in Scotland soon too.
But in England you can still get plastic carriers for free in most shops.