For a pre-award audit, it's automatically triggered if the contract is over $2 million. Otherwise, it can be triggered voluntarily, but it's the $2-million threshold.
A post-award audit is at the request of the contracting authority, of the client department or of ISC, which would be quite rare, as we don't have oversight of the contract during the administration or the life of the contract.
A discretionary audit would similarly be requested by the client department or the contracting authority if there was rationale or reason to consider that it might be useful.