Things You'll Need
Instructions
Practice the amount of pressure to use with a toothpick on a note of lesser (or no numismatic) value first. This can be an old one dollar bill.
Launder (literally) the money with regular clothing. Tie it in a cloth bag first. This is not advised for collectors, but it has been used by the Treasury Department as a way to clean soiled bills. Afterward, the bills were pressed, dried and returned to circulation.
Use hairspray or apply rubbing alcohol on the opposite side of the ink mark. Press the bill down on a wet white cloth. Slowly outline the ink stain with a toothpick; do not press hard. Use the toothpick as a way to apply specific pressure; do not rub.
Use Oxyclean detergent using the same method in step 3. This works well and is easy on paper. Use a paste, and apply with a toothpick.