What is the ruling on money acquired from issuing fictitious invoices to other companies to adjust their tax files, without the knowledge of the owner of the company I work for, but in coordination with my manager and sharing this money?

It is not permissible for an employee to take a percentage from companies in exchange for issuing invoices from his company without the knowledge of the employer, because he is a private employee who receives a salary, and it is not permissible for him to take money in addition to his salary except with the approval of the company owner.