Rubbing Alcohol
If you use your patent leather bag on a daily basis, then there are chances that it is marked by pen marks. One way to get rid of this is to use a solution of two parts of rubbing alcohol and one part water. Use a cotton ball to apply this mixture to all those areas on the bag that has pen marks on it and allow the area to be saturated completely. Once this is done, you can use a piece of cloth to erase any remaining spot of pen mark on the bag.