Question Summary:
May I create web tools or applications for people that want to calculate interest?

Question Detail:

 
I am a programmer and a web developer and I create websites and tools for businesses and individuals. I often find myself having a chance to work with people who wants web tools that calculates interest or mortgages. Although, they are not directly related to any bank or do not provide loan themselves(they just want to calculate or advise users), I avoid them in fear of earning haram money. Is it allowed for me to develop such interest and mortgage calculator applications? Does it promote evil?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
Although accountants only calculate and advise users, your job is developing an application that will be used for the sole purpose of interest. As Muslims, we are averse to interest. Therefore, our advise is to continue your usual habit in avoiding such people in order to abstain from developing such applications.^[1]
And Allah Ta’āla Knows Best
AbdulMannan Nizami
Student Darul Iftaa
Chicago, IL, USA
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net