Here are examples shared that comes from a company we sell to:
Example no. 1 - "If I make a full prepayment, the Note Holder may charge me for the privilege of prepayment if I prepay the loan in the first 36 months after the date of the loan. The prepayment penalty shall be an amount equual to 5% of the principal balance prepaid."
Example no. 2 - "If I make a full prepayment, the Note Holder may charge me for the privilege of prepayment if I prepay the loan in the first 60 months after the date of the loan. The prepayment penalty shall be an amount equal to six months advance interest on the amount of the prepayment that, when added to all other partial prepayments during the twelve-month period immediately preceding the date of the full prepayment, exceeds 20% of the original principal amount of this Note."
The language will vary by state.