The government in Northern Ireland have just introduced a tax on plastic bags, which means that people there will have to pay 5p every time they need one.
The money will be used to fund environmental projects.
Wales introduced the measure two years ago, and it's expected to come into place in Scotland too.
But in England you can still get plastic carriers for free.
It's thought that charging for the bags will make people think about re-using them, and that it will be better for the environment.