Example:

A contractor bidding to a project owner for a contract and the chief executive of the project owner agree to a corrupt arrangement under which the chief executive will ensure that the project owner awards the contract to the contractor.  No payment will be made by the contractor to the chief executive at that time, so any audit or investigation of the procurement process would not uncover any suspicious financial transfers.  However, once construction of the project commenced, the chief executive would ensure that some major variations to the contract scope of work were issued, and that a highly profitable price for the contractor would be agreed in respect of these variations.  The contractor would then make secret payments to the chief executive out of the variation profits. 

Explanation:

The above example illustrates one of many methods of concealment of bribes.  Many project owners’ controls over project construction, including the issuing of variations, are much lower and less effective than their controls over procurement, therefore making it more likely that corrupt variations can proceed undetected.  There is also normally no competitive pricing process in relation to variations (unlike in the original procurement process) so verifying whether the contractor’s price for the variations is reasonable can be difficult.  

In the above case, the contractor would be guilty of bribery and fraud, and the chief executive of bribery, fraud and abuse of power.  The fraud would be the issuing of false, unnecessary and/or over-priced variations for the purpose of enabling additional profit for the contractor and a bribe payment for the chief executive.