In recent years, deficiencies in construction documents has become a common problem in the construction industry. In most cases this leads to financial consequences, both for clients and building contractors. The risk of financial consequences can be minimized if the deficiencies and errors are eliminated before the construction phase or if it’s detected in an early stage of a project. Within Peab Skellefteå, a lot of time, energy and money are spent to investigate the deficiencies and errors in construction documents. This mostly occur in the construction phase, since that is where the deficiencies and errors usually are discovered. Previous studies concerning the same area indicate that financial consequences is a result of inadequate construction documents and alteration and additional works, but none of the studies includes further investigation concerning how it practically appears in projects and in what way it affects the client’s and building contractor’s economy. Based on this, the purpose of the report has been formulated: The purpose of the master thesis is to investigate and understand how inadequate construction documents affects individual construction projects in terms of economy. Based on the results from the interviews, recommendations will be proposed regarding how the risk of financial consequences can be reduced to help entrepreneurs avoid these types of situations. The content of this report is essentially based on interviews with nine participants, either site managers, construction engineers or purchasers from Peab Skellefteå. Theory from previous studies is also used and the report is limited to traditional contracts. The results of the interview study revealed that both the building contractor and the client have been negatively affected in terms of economy in project 1–6. It is hard to report accurate numbers, since inadequate construction documents might affect the next work stage, contract rate, time that should have been spent doing something else and the time spent to investigate deficiencies and errors, which can be difficult to prove. Some costs could be deduced to the discovered deficiencies and errors, see Table 1. Generally, it’s stated that deficiencies in construction documents entails financial consequences for both entrepreneurs and clients. The respondents explain that the drawings are the most problematic construction document and that’s where most errors are discovered. The parts of the drawings that’s usually inadequate is piercings, fittings, inner walls, details, attachments and contradictory information. Deficiencies typically connected to financial consequences for the building contractor is piercings, reinforcement, fire sealing and time spent investigating the deficiencies. For the client, typical deficiencies connected to financial consequences are lack of foundation- and ground investigation, quantifying errors, when incorrect dying times leads to extra costs and additional work. The respondents’ suggestions for improvement in collaboration with the author’s own thoughts is the basis of the given recommendation. The main potential improvements for designers are to review construction documents more accurate, increase their knowledge about production and materials, work with BIM-coordination and be receptive to feedback. Clients should check the coordination, increase their knowledge about work steps and materials and have consistent solutions through the project. Building contractors should have coordination meetings with designers, clients and installers, make an appropriate number of tender calculations, provide feedback to designers and clients, use the question/answer-method, design a useful contract administration and increase the review of contract documents for the often-deficient parts.