(1) The amount of the claim to remuneration for the expense and effort that, as a consequence of the customer’s order pursuant to section 650b (2), have increased or decreased is to be identified based on the factually required costs, with reasonable surcharges being added for general administrative costs, business risk and profits. Where the contractor’s duty of performance also includes planning the building or the outdoor facility, the contractor will not be entitled, in the case governed by section 650b (1) sentence 1 no. 2, to a claim to remuneration for increased expense and effort.
(2) In calculating the remuneration for the change order, the contractor may take recourse to the calculation approaches used in the initial costing calculation that has been lodged as contractually agreed. It is presumed that the remuneration updated on the basis of the initial costing calculation corresponds to the remuneration pursuant to subsection (1).
(3) Unless the parties have reached an agreement on the amount, or unless a court of law hands down a decision stipulating otherwise, the contractor may, in calculating part payments agreed upon or part payments owed under section 632a, assess 80 per cent of an additional remuneration set out in an offer pursuant to section 650b (1) sentence 2. Where the contractor opts to proceed in this manner and no court decision is handed down that stipulates otherwise, the additional remuneration owed pursuant to subsections (1) and (2) will be due only following acceptance of the work. Payments under sentence 1 that are in excess of the additional remuneration owed pursuant to subsections (1) and (2) are to be repaid to the customer and are to bear interest from the date of their receipt by the contractor. Section 288 subsection (1) sentence 2, subsection (2) and section 289 sentence 1 apply accordingly.