This is a sample of the front of the newer 500 rupee note. It matches with the critieria of all genuine notes as put out by the RBI the see through number in the left margin, the watermark, the thick shiny security thread and so on. By clicking on the link you can check the points.
The note below can be mistaken for fake by an over zealous person trying to check for genuine notes. It is the front of a 500 rupee note and it looks quite different from the one above. However, this note, signed by the RBI Governer Bimal Jalan is absolutely genuine. The note has a thinner shiny vertical band (security thread) unlike the newer note which has a thicker one, and it does not have the see through number (register). Instead it has a flower design in the left margin. These notes were printed between November 22nd 1997 to Sep 6th 2003. Why was their design changed? The attempt was to make the 500 rupee notes difficult to copy.
Does this mean that cheats and forgers can make fake notes of this type easily? Perhaps, but now it is difficult because the genuine notes will look old as they are used notes. You can find that out by just looking at them. They will never be crisp and new.
The one below is the older 500 rupee note. No date of printing there, but it is a genuine note so no need to worry. As mentioned above, such notes will have a used look and that is how you can be sure they are genuine.
Related Images: Indian Coins - Paise or Rupee Notes Images or check out all images filed under the label of Currency, which will have photos of currency notes from the U.K, U.S and other countries.
NOTE on 1st Jan 2015: The Indian government is soon discontinuing with the older notes. So anyone who has the older notes, the ones without the date of printing on them, please turn them over to your bank. Today they are legal tender, but they are being phased out so best return them.
Note on 13th of November 2016: On the 8th of November the Prime Minister announced that all ₹500 and ₹1000 notes will cease to be legal tender from midnight. New notes will be issued.