The liabilities which are to be paid of at the time of dissolution of firm are called fixed liability. For example: Capital, Reserve and Surplus etc.Though, as a special case the amount can be withdrawn against the capital by the proprietor or the partners and shares also can be redeemed by the company but not on frequent basis.
The reserves and surplus also can be utilized for a particular purpose in certain circumstances but it also happens very rare. But the person who has contributed in the capital of the company, can not force the company to pay the amount of his investment whenever he wishes. Therefore, the capital and reserves and surplus are come under category of fixed liabilities.