158. No Government servant may, without previously obtaining an extra appropriation incur expenditure in excess of the amount provided for contingent charges under the head of the account concerned, and when a Government servant exceeds the annual appropriation he will be held personally responsible for the excess. In the case of contract contingencies disbursing officers have full liberty to expend the sanctioned grant under each major head, but excess expenditure over a contract grant can only be permitted by Government. It must be distinctly understood that when a contract allowance is once fixed it cannot, under any circumstances whatever, be exceeded without the previous sanction of the Government and that this will only be given in cases of extreme necessity. It will not be sufficient to show that unavoidable or unforeseen expenditure has to be incurred in excess of the provision under one or two items ; it must be proved to the satisfaction of the Government that the contract sum, as a whole was insufficient; and that the excess could not be met by strict economy under other heads. When a number of items are included in a lump grant saving with good management, will always be possible under some heads ; and Government servants must learn to limit their expenditure by the sum placed at their disposal. An additional appropriation, even if made, is liable to be retrenched from the appropriation of the following year.