Procurement contracts are often renegotiated due to changes that are initiated after the award – either by the public buyer or the private contractor. Using novel, unpublished data on post- award price adjustments in Swiss construction procurement, I show that renegotiation imposes significant friction and adaptation costs. Regressions suggest that bidders respond strategically to contractual incompleteness (submitting low initial bids, relying on later price adjustments) and that adaptation costs are an important determinant of their bids. The paper empirically tests factors that influence post-award price adjustments and shows that adjustments are influenced by the complexity of the project, competition and buyer experience. The finding that competition increases the likelihood of post-award adjustments is novel and strengthens the narrative that even though competition lowers bid prices, it does not necessarily lead to lower final prices. Linking this finding with the choice of the award procedure, the empirical analysis suggests that competition is U-shaped, indicating that the selective procedure with a limited number of bids is the least efficient procedure, compared to open auctions and private negotiations. The results also show that contracts awarded by experienced buyers are associated with lower price adjustments and that ex-post price adjustments are more prevalent in services procurements, which could be linked to a lack of cost reduction incentives in service contracts. The analysis is complemented with construction contracts awarded by the Swiss Federal Railways, indicating that framework contracts have potential to minimize ex-post adjustments for standardized procurements. Survey responses from procurement officials and construction firms round up the picture and shed some light on post-award costs and compensation schemes used in practice. The paper concludes with a discussion about the results’ implications for procurement policy.