ESI Fund investment rules require Central Government oversight, controlled asset changes, and crediting of all investment income. The Employees' State Insurance Fund is to be invested by the Corporation in accordance with Central Government guidelines, with losses and expenses charged to the Fund and profits credited to it. The Corporation may open necessary accounts, vary or realise investments, and must obtain prior Central Government approval where a change is likely to cause loss. The Central Government may direct vacation or prohibition of investments in specified securities, land or buildings, and all investment income must be credited to the Fund.