Shopping just got a bit more complicated. Sainsbury has launched a new Nectar prices offering to match a similar one from Tesco’s Clubcard.

Both schemes require customers to use the loyalty cards when they shop to get access to around 300 prices that are up to 50% below the normal shelf prices.

It means customers, who do not have the cards or apps or forget to use them at the till, pay more. Anyone without the loyalty cards/apps effectively subsidises those who use them.

In addition Sainsbury offers weekly individual prices on about ten products to Nectar card holders. The information is provided on the app and is not on the shelves, making it easy to miss the offers.

Meanwhile there is more confusion on the shelves. Supermarkets are required to tell us what products cost per unit. But they do not always get it right.

The picture shows a pack of 44 Arial pods. The pack weighs 1.0208 kg. The price per kilo is said to be £9.98. Therefore it should cost £10.19. The price on the shelf label is £12.50.

Next to it on the shelf was another pack of 44 Arial pods weighing 0.858 kg. The price per kilo is said to be £11.83. It should cost £10.15. The price on the shelf label is £12.50.

The price per pod was nowhere to be seen but at 44 pods per pack and the same unit price was 28.4p.

Next to that was a pack of 25 pods for £6 - 24p per unit. The weight on the pack says 460g. This works out at £13 per kg.

We all have to take our calculators with us and allow plenty of time. Anyone would think the stores were trying to confuse us when we seek the best value.