Slide dollar bills into the plastic sleeve that comes with the kit. Tear off any unused plastic sleeve and discard.
From the closed end, tightly roll up the plastic sleeve filled with money.
Open the box and separate the lid and clip. Open the clip and place it through the slot in the lid. Place the end of the plastic sleeve in the clip and snap it closed.
Place the roll of money into the box, securing the lid. Push a topper into one of the holes on the clip. Test it to make sure it pulls up easily, then open the box, reroll the money, and replace the lid and topper.
Remove extra frosting from top of cake and save for later.
Cut out a piece of cake that's the same size and shape as the box. Remove the cake and place the box in the hole, pressing it down until it's just below the surface of the cake.
Use the extra frosting you removed to cover the box and smooth out the frosting on the entire top of the cake. Add extra sprinkles, candies or berries.
The cake is ready to go! To reveal the money, just pull up on the topper.