Assalam, I had invested money in oil manufacturing plant where the owner gives me fixed return on invested money. The agreement is working since three years. Is it halal to accept that income according to Islamic view?
As far as I know, giving an amount of money to someone or even companies or other job by the intention of obtaining solely interest would not be Halal. because perhaps we can term it as Riba (interest). Since you pay a specific amount of money that you constantly obtain interest, not disadvantage. So it could be considered as Riba. Then as far as I know, you should write a contract that you be partner in both interest and disadvantage, not solely in the interest.
Your profits must be associated with the performance of the business you've invested in. Otherwise if you've used the money to obtain the right to even more money then that is interest.