Is it obligatory to return the salary increase that was taken without the partners' knowledge, and what is the amount that must be returned to each partner, whether it is the full amount or one-third of it, especially after the company's liquidation and the inquirer's desire to absolve himself?

A partner increasing his own salary without the permission of his partners is not permissible and constitutes a betrayal. This is based on the saying of Allah the Almighty in the Hadith Qudsi: "I am the third of the two partners as long as one of them does not betray his companion. If he betrays him, I depart from between them." And due to the saying of the Prophet (peace be upon him): "On the hand is what it has taken until it returns it," and "It is not lawful for a person to take anything from his brother's wealth except with his willing consent." Therefore, what was taken unjustly must be returned and divided among the partners.