According to this article around half of people who buy their groceries online receive the wrong items. A questionnaire found that 45% had at least one of their items substituted for another product and 15% received something they had not ordered. I have used the Sainsbury’s Online for about five years now and whilst it did used to be fairly unreliable with missed deliveries and broken down vans over the past couple years it has been quite good. I usually receive the correct items with few substitutes and can only ever remember receiving items I haven't ordered once. On that occasion I received a bag of cigarettes (I don’t smoke) but the situation was quickly resolved when I called the store and upon realising the mistake they collected them and brought my bag of shopping in its place.