1. Under the terms of the contract in force, participants are entitled to the benefit (supplementary retirement pension) when they 'retire due to old age or disability';
2. If the right is acquired, the rule can only be changed if it is waived, unless, prior to the acquisition of the right, there is an act that invalidates what is stated in the constitutive contract, such as, for example, the employment contract, either the contract itself or the internal service order of the company, or even an individual communication sent to each and every participant;
3. Since the pension scheme is established by a unilateral act of the undertaking, it may be amended by a unilateral act, provided that, on the date of that amendment, no acquired rights are infringed;
4. As to the form of the amendment, although it does not expressly refer to Decree-Law no. 12/2006, of 20 January, it follows that the pension plan must take the written form (article 21, no. 1 and 2, subparagraph g) of Decree-Law no. 12/2006), therefore, any amendment to it must necessarily take the same form (articles 219 to 221 of the Civil Code).