1. What is the ruling on selling software systems that are designed within the company and by the employee himself, knowing that the employment contract does not prohibit this, and the company manager feigns displeasure? 2. What is the ruling on designing systems for the tax authority that specialize in calculating taxes, especially if refusing this work will cause discord within the company? 3. What is the ruling on designing systems for banks that calculate interest and other banking systems, knowing that there are scientific and material benefits from this work?

The default ruling for creating software systems is permissibility. However, if the programs are for a forbidden matter or assist in something forbidden, then they are impermissible (haram), due to Allah's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression."

Accordingly, creating programs for usurious banks that assist in usury, or for tax authorities that assist in (unlawful) taxes, is forbidden. Maintaining these programs falls under the same ruling.

As for your work in the company, there is no harm in it, provided that you do not work on or maintain a program that involves something forbidden or assists in it. If you are forced to do so, then leave them, and remember: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect."

As for selling these systems for your own benefit, if you copy programs developed by the company with its funding and sell them for your own gain, this has been detailed previously in Fatwa No. 70833.