Are we sinful for renting accounting software to companies or shops that deal in permissible matters, but they enter prohibited substances into it and use it in their sale, and is it obligatory for us to stipulate that these substances not be entered?

It is forbidden to sell anything that leads to the unlawful if the seller knows that the buyer intends to use the sold item for a sinful act. Some scholars equate strong suspicion with knowledge, but doubt does not necessitate prohibition. Therefore, renting out the program is not forbidden as long as you do not know that the renters intend to use it for something unlawful. There is no need to explicitly state that the program should not be used for unlawful purposes, as this is already a religious obligation. However, if you know that the program will be used for something unlawful, but its primary purpose is permissible and the unlawful aspect is minor and incidental, then renting it out is not forbidden, as what is tolerated implicitly may not be tolerated explicitly.