MUMBAI, Dec. 18 -- The Securities and Exchange Board of India (Sebi) on Wednesday introduced a series of regulations for mutual funds, with changes to expense structures likely to have the most direct impact on investors.

Here's a closer look at what these rules entail and how they could affect the cost of investing in mutual funds.

At the heart of the reforms is a reworking of the expense ratio framework. Aiming to improve transparency in how expense ratios are charged, Sebi has introduced a new concept called the Base Expense Ratio (BER) and explicitly excluded statutory levies from its scope.

Charges such as securities transaction tax (STT), commodity transaction tax (CTT), GST, stamp duty, exchange fees, and Sebi fees will now be l...