The designer assists the client during the phase of entrusting of the work. If private, it is sufficient to draw up a formal document with special terms of contract which, based on indications of the general contract, defines the relationship between client and company. In the first section are defined the general elements of the contract, such the amount of the work, the duration, the burden of the customer and of the society, the regulation of variants and sub-contracting, the guarantees during the construction and at works completed, site supervision and trail, payments , resolution of disputes.

The second section, technical, reports the work to be performed by ways of intervention, supplying and quality of materials, measurement of manufactures, construction.
In case of public contract, the designer needs to ensure that, together with the head of the processing contracting station, the tender documents (contract, specification, scheme contract, various attachments). The interventions on the state goods and/or paid by it are governed by the Public Procurement Code, which contains all the rules, constantly updated regulations. The tenders are assorted, depending on the object, the working class, the amount of the works, the category of funding. If the race also includes the preparation of a detailed executive planning based on the final one edited by the administration, this is known as contract competition.