What is the ruling on money acquired from purchasing non-documentary invoices that are not approved by tax authorities in order to reduce profits, taking into account the commission distributed among the parties, and what should be done with the money if it is unlawful?

The money taken from the company without its knowledge is unlawful (haram) and must be returned to it. The questioner should advise his friend and clarify the unlawfulness of their actions. If the friend does not accept, then the questioner must absolve himself by returning the company's right to it.