Bake the chocolate cake according to package directions in a 9×13-inch pan. Let cool for 5 minutes.
Use the handle of a wooden spoon to poke holes all over the warm cake. Pour sweetened condensed milk evenly over the cake, followed by the caramel topping.
Allow cake to cool completely, then spread whipped topping over the top. Sprinkle with toffee bits. Refrigerate for at least 2 hours before serving.