In order to ensure that there is compliance throughout the contracting process, first there is a certification by the vendor that they will meet the 33% requirement.
Second, that is put into the terms and conditions of the contract, and those terms and conditions have to flow from the prime to the subcontractors. That requirement is also in the subcontracted contracts.
Third, it's the responsibility of the client department or the department that's receiving the good or service to verify throughout the life of the contract that the compliance to the 33% value criteria is met.
Finally, there's an audit option, and that would be a discretionary audit that could be requested, if required, at any time. As well, a post-award audit could be requested as a final way to verify compliance, should there be concerns at the termination of the contract that the 33% may not have been met.