I believe your query pertains to the Indian Law context and not Pakistan. If your establishment/company is an "Industry" as defined in Section 2(j) of the ID Act 1947 (India), please refer to the provision under section 9A of the ID Act which is given verbatim.
9A. Notice of Change - No employer who proposes to effect any change in the conditions of service applicable to any workman in respect of any matter specified in the Fourth Schedule shall effect such change:
- Without giving to the workmen likely to be affected by such change a notice in the prescribed manner of the nature of the change proposed to be effected; or
- Within twenty-one days of giving such notice.
Provided that no notice shall be required for effecting any such change:
- Where the change is effected in pursuance of any settlement or award; or
- Where the workmen likely to be affected by the change are persons to whom the Fundamental and Supplementary Rules, Civil Services (Classification, Control and Appeal) Rules, Civil Services (Temporary Service) Rules, Revised Leave Rules, Civil Service Regulations, Civilians in Defence Services Classification, Control and Appeal) Rules, or the Indian Railway Establishment Code or any other rules or regulations that may be notified in this behalf by the appropriate Government in the Official Gazette, apply.
I am also providing a list of items under the Fourth Schedule for your reference:
1. Wages, including the period and mode of payment;
2. Contribution paid or payable by the employer to any provident fund or pension fund or for the benefit of the workmen under any law for the time being in force;
3. Compensatory and other allowances;
4. Hours of work and rest intervals;
5. Leave with wages and holidays;
6. Starting, alteration, or discontinuance of shift working otherwise than in accordance with standing orders;
7. Classification by grades;
8. Withdrawal of any customary concession or privilege or change in usage;
9. Introduction of new rules of discipline or alteration of existing rules, except insofar as they are provided in standing orders;
10. Rationalisation, standardization, or improvement of plant or technique which is likely to lead to retrenchment of workmen;
11. Any increase or reduction (other than casual) in the number of persons employed or to be employed in any occupation or process or department or shift, not occasioned by circumstances over which the employer has no control.
I hope this answers your query.