The plastic bag levy, which the government estimates could net charities up to £73m a year, has come into force in England.
From today, large retail chains will be required to charge 5p for single-use plastic bags in a bid to reduce the number that are handed out, with many retailers pledging to give the extra cash to good causes.
Although a charity donation is not mandatory, the government guidance for retailers says: "Once you’ve deducted reasonable costs, it’s expected that you’ll donate all proceeds to good causes."
It says that reasonable costs include changing till systems, training staff, communicating the policy to staff and customers, getting expert advice and administering the donations, but not the cost of the bags themselves.
The levy comes after similar schemes were introduced in Wales, Northern Ireland and Scotland. It covers all retailers employing more than 250 staff.
The supermarket giants Tesco, Waitrose, Morrisons and Sainsbury’s have all promised to give the proceeds away.
A spokeswoman for Sainsbury’s said profits would be "donated to local good causes".
She said: "This will be done on a store-by-store basis, so charities are advised to contact their nearby Sainsbury’s."
In a statement on its website, Tesco said it would be offering customers the chance to nominate and vote on the six local causes in each of the 432 regions they would like to see receive between £8,000 and £12,000 a year through the bag charge.
The statement said administration of local funding would be handled by the environmental improvement charity Groundwork.
Rebecca Shelley, group communications director for Tesco, said the company would "work together with our customers to make sure the millions that will be raised from the bag charge go towards making a real difference for our local communities".
A spokesman for Waitrose said: "Every penny will go to a community and environmental fund. This is an internal fund set up specifically for the proceeds of carrier bag charging legislation in England – every year it will be decided where the proceeds are donated.
"All of the proceeds from carrier bag charging (less VAT) will be donated to good causes. We won't make any deductions for administration costs."
He said it was unclear how much money would be raised, because it depended on whether the charge persuaded people to use fewer bags.
Morrisons plans to donate the proceeds of the charge to its own charitable foundation, which will offer grants to local charities around the country.
Martyn Jones, group corporate services director for Morrisons, said: "The charge will be a boost for local charities across the country and help them to deliver projects that will make a real difference in their communities."
In a statement on its website, Morrisons said it would also donate some proceeds to its charity partner, the hospice charity Sue Ryder, and funds raised online deliveries would support a bag recycling initiative.
A spokeswoman for the British Heart Foundation, one of the largest operators of charity shops in the UK, said it had not been affected by the policies in the other home nations.
But she said the charity was expecting to plough any money raised through the scheme into its own funds.