Hell Bank Notes are a special form of joss paper, an afterlife monetary paper offerings used in traditional Chinese ancestor veneration, that can be printed in the style of western or Chinese paper bank notes.
In order to ensure that spirits have lots of good things in the afterlife, their relatives send them paper presents, and one of the things that are usually sent to ancestors are Hell Bank Notes--money to spend in the afterworld.
In some mythology, the Hell Bank Notes are sent by living relatives to dead ancestors to "bribe" the King of Hell for a shorter stay or to escape punishment. In these more modern times, the creation of "Hell Bank Note Credit Cards" have become very popular. The designs on these "credit cards" vary from the very simple (with just a basic "VISA" stamped on a gold cardboard card), to very elaborate (with custom artwork and names).
Regardless of the presentation, Hell Bank Notes are well known for their outrageously large denominations, ranging from $10,000, $100,000, $1,000,000 or even $500,000,000; the Chinese afterlife is apparently subject to hyperinflation. On every bill, it will usually feature an image of the Jade Emperor, and his signature (Yu Wong, or Yuk Wong) countersigned by Yanluo, King of Hell (Yen Loo). On the back of each bill, it features a portrait of the bank of Hell.