In the case of a 25kg prepack, the cost of the 25kg prepack is the selling price, the unit price will be twice the selling price and both prices must be stated. The selling price has to be given to the consumer when the product is offered for sale, e.g. it is in a shop ready for sale, on a lorry or when a customer telephones to place an order. Solid fuel has to be made up in a prescribed quantity e.g. 25kg or 50kg for open sacks, and multiples of 5kg for prepacks, under the Weights and Measures Act 1985. There is an exemption from the requirement to unit price for small shops - that is one with a floor area for retail sales not exceeding 280 square metres. This could include small garage forecourts.
Itinerant traders are also exempt from the requirement to unit price.
However, if you send a lorry out loaded with coal sacks all of which are fulfilling pre orders - you do not need to carry a separate price list, unless Byelaws apply. If, however, you have all or any bags available for sale by hawking, you do not need to display unit prices, but you do need to display a full comprehensive price list of all the goods you are offering for sale on the vehicle. If the selling price is given in an advertisement then the unit price must also be given. Therefore if you offer 25kg prepacks and you indicate the selling price of the 25kg prepacks you must also indicate the unit price. If there is a change to the VAT rate, you must indicate that the prices given are subject to change if old price lists are still being given out.