22Details of prime cost items and provisional sums must be set out in writing

22 Details of prime cost items and provisional sums must be set out in writing If a domestic building contract provides for any prime cost items or provisional sums, the builder must not enter into the contract unless— (a) in the case of a major domestic building contract, the contract contains a separate schedule for each item or sum that sets out— (i) a detailed description of the item or of the work to which the sum relates; and (ii) a breakdown of the cost estimate for each item or sum (showing at least the estimated quantities of materials that will be involved and the unit cost to the builder of the item or sum); and (iii) if the builder proposes to charge any amount in excess of the actual amount of any increase to the item or sum, how that excess amount is to be determined; (b) in the case of any other contract, the builder gives the building owner before entering into the contract a written document that sets out for each item or sum the information required by paragraphs (a)(i), (ii) and (iii).