23. Is there a ban on political parties engaging in commercial activities?

"A political entity may not realize income from promotional, and/or commercial activity." 
Article 14. Law on financing political activities, 2022.

There are however two more articles in same Law on financing political activities regulating this field further. Article 7 says “Private sources of financing political activities comprise membership dues, donations, inheritance, legacy and income from property.” 
Furthermore, article 11 of same law regulates acquisition and income from property of the parties: “Assets of a political party comprise real property and movables. Assets referred in paragraph 1 of this article serve only for political activity and other allowed activities of a political party, in accordance with law. A political party acquires property through purchase, inheritance and legacy. A political party that acquires real property with funds collected from public sources, may use such property exclusively for the implementation of its political activities. Real property referred to in paragraph 4 of this Article may not be alienated by a political entity without compensation or at a price lower than the market price, according to the assessment of the competent tax authority. Income from property is the income realized by a political party from sale of real property and movables, lease of real property in its ownership and interest on deposits with banks and other financial organizations in the Republic of Serbia.
 

There are provisions that political parties are allowed to engage in either commercial or business activities.