Mutual fund distributors earn their commission through what is known as a "trail commission" or "trailing commission." This commission is a small percentage (typically around 0.5% to 1%) of the assets under management (AUM) of the clients' investments in the mutual funds they distribute. 

The mf distributor commission is paid by the asset management company (AMC) to the distributor for as long as the client's money remains invested in the mutual fund. In addition to the trail commission, distributors may also earn upfront commissions, which are one-time payments based on the initial investment amount. 

These upfront commissions are typically higher than the trail commission but are becoming less common due to regulatory changes aimed at improving transparency and reducing conflicts of interest. Overall, the commissions earned by mutual fund distributors can vary based on the mutual fund scheme, the amount of assets they manage, and the fee structure of the AMC.