What additional audit procedures must be performed where events or conditions have been identified that may cast doubt on the entity going concern?

Review management’s plans for future actions based on its going concern assessment - which implies ask for approved by management budgets and even a5 year plan. A written representation from management will bring comfort but not sufficient. Address all the concerns and mainly the issues regarding liquidity, credit risk, challenge the cash-flow budget and understand if it is realistic and based on existing contracts. Cases of going concerns have a number of causes and relate to each of them. It could be the political environment, economic crisis particularly for the industry where the company operates, lack of cash, captive to certain clients who will cancel the contracts, high debt which can't be prolonged by creditors and inability to pay back, etc. If each of these risks are properly understood and evidence is gathered to show if going concern is threat then the auditor should reach a reasonable conclusion.