In contrast to a unit price contract, a lump sum contract does not depend on the services actually rendered. Rather, the parties agree on a binding lump sum price for the commissioned services right at the conclusion of the contract. Apart from the exception of the lapse of the basis of the contract, it does not matter whether additional or reduced quantities are actually provided.
However, if the principal unilaterally demands a service not provided for in the contract, the contractor is entitled to special remuneration irrespective of the lump sum agreement.