Is it permissible to work for a computer software company that designs sales programs dealing with credit cards to store card numbers and amounts? And is this considered aiding in the sale of impermissible items, such as cigarettes, if some companies use it for this purpose?

The basic principle concerning software development is permissibility, unless it is intended for a forbidden purpose or assists in one, based on the Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." Therefore, developing sales software is permissible, but it is forbidden to create a service within the program that assists with usurious credit cards. However, if the program can be used for both lawful and unlawful purposes, there is no harm unless it is known that the company will use it for unlawful purposes. This issue relates to aiding in what is forbidden, as it is prohibited to sell what is intended for unlawful purposes when one knows or strongly suspects it, like suspecting someone will use grapes to make wine. As for working at the company, there is no harm in it, provided one does not work on or maintain a program that is forbidden or assists in something forbidden. If compelled to do so, one must leave the job.