Yes, starting from 1st July 2020, the government has started to levy a charge called "Stamp Duty" of 0.005% on the purchase (investments/purchase transactions) of all mutual fund units. 

This is deducted from the amount you invest and the purchase of units happens after this deduction.

For eg. If you invest Rs. 1000 in a fund, Rs. 0.05 (0.005% * 1000 = 0.05) will be deducted as stamp duty and the remaining amount, i.e. Rs 999.95 (1000 - 0.05 = 999.95) will be invested.

Please note that the stamp duty is deducted only at the time of purchase of units (including SIP purchase) and not at the time of redemption.

There can be some charges and/or taxes when you redeem (withdraw money) from your investments. You can read about it in this FAQ.