From today, large shops will have to charge you 5p for every carrier bag you use. Here's your guide to how the rules work.

Items considered a health or safety risk are exempt, including raw meat, razor blades and flower bulbs, and shops with fewer than 250 members of staff don't have to charge unless they want to.

Which stores do the rules apply to?

Any business that sells or delivers goods. However, retailers with fewer than 250 members of full-time staff nationwide don’t have to charge unless they wish to do so.

Which types of bags are being charged for?

Any unused, plastic bags which have handles and are 70 microns thick or less. Sealed packaging isn’t covered by the charge.

Which items will I still get a free bag for?

Uncooked fish and fish products. Uncooked meat, poultry and their products. Unwrapped food for eating - such as chips or food sold in containers that might leak. Unwrapped loose seeds, flowers, bulbs, corns, rhizomes (roots, stems and shoots, so that includes ginger) or goods contaminated by soil. Unwrapped blades, including axes, knives, and knife and razor blades. Prescription medicine Live aquatic creatures in water.

So can I just put a steak in each bag and get it for free?

If even one non-exempt item is placed in the bag, cashiers must charge 5p.

What about supermarket online shopping?

You will be charged for the bags your shopping is delivered in. Most supermarkets are introducing a flat charge of around 40p per delivery, but some, like Ocado, will refund you for each bag you return.

What else is exempt?

Bags from shops in airports, or on board trains, aeroplanes or ships. Items considered as sealed packaging for mail order and click-and-collect orders. Returnable multiple reuse bags (bags for life) - although these are usually charged for anyway. Bags given to you containing free promotional material. Bags used for a service where there’s no sale of goods e.g. dry cleaning, shoe repairs.

Who will benefit from the extra money raised from 5p bag sales?

Retailers are being told to donate all proceeds from carrier bag sales to good causes, but it is for them to choose what to do, and which causes to support. They will need to report to the government about what they do with the money, and it will be published yearly.

Boots will give all UK proceeds to Children in Need. Morrisons will give money to the Sue Ryder hospices and Superdrug is donating the money to support Marie Curie Cancer Care.

However, the government is set to make £19m a year from the VAT attached to the sales of bags.

How will the bag charge impact the environment?

Since the scheme was launched in Wales in 2011, the number of plastic bags given away by shops has fallen by 71 per cent. In Scotland, the number of bags handed out by supermarket dropped by 147 million.

Last year British supermarkets gave out 8.5 billion plastic bags, an increase of 200 million on the previous year. The new 5p charge is expected to reduce the number of plastic bags, which will be beneficial for the environment.