Is earning a 15% profit from every transfer made by a user I invited to a website for transferring money between e-banks (whereas the transfer fee is 5% or 8%) permissible or forbidden?

Transferring money for a known percentage of the transferred amount is permissible, as is dealing with the website and benefiting from the commissions it offers. Appointing an agent for a known fee is also permissible. Scholars have differed on whether the commission can be a percentage; the majority stipulate that the fee must be a known amount, while some have allowed it to be a percentage of what is obtained.