Concentration limits in mutual fund debt portfolios restrict exposure to a single issuer, with board approvals for higher exposure. Mutual fund schemes face an issuer-level debt concentration limit on investments in debt instruments rated not below investment grade by a Board-authorised credit rating agency, with a provision for higher exposure subject to prior approval of the Board of Trustees and the asset management company's Board of Directors. Exemptions include Government securities, treasury bills and collateralized borrowing and lending obligations; mortgaged backed securitised debt may be included within the limit if similarly rated. Existing schemes must conform to the revised limits within a timeframe and manner specified by the Board.