Customers complained that the prices charged for online groceries when delivered could be different to those advertised on the website.
The OFT found that, apart from Ocado, supermarkets used guide prices to show the price of goods on the day that customers placed their order, even though the actual price the customer would pay would be the price of goods on the day that they were delivered.
Asda, Sainsbury, Tesco, and Waitrose have all agreed to provide upfront information about their guide price policies, how the online shopping process works and to ensure that special offer online prices are treated as firm prices.
Ocado, which offers fixed prices except for goods sold by weight, has agreed to provide clearer information about prices for catch-weight goods.
John Fingleton, chief executive of the OFT, said: “We welcome the supermarkets' improvements to the information available to customers buying groceries online. Customers have a right to clear and transparent information upfront when making their buying decisions.”