Error

Errors are major stamp production mistakes that have been sold by the post office as normal. The latter point is important since there have been many instances of defective stamps being smuggled out of printing plants or defective stamps being taken from their trash. Those items are known as printer's waste. Errors have also been deliberately made for sale to collectors at a premium price, notably in recent years.

These mistakes have to be significant to be considered as an error philatelically. Something like completely missing a color, completely missing perfs constitutes an error. A slight shift in a color or perfs, partial missing colors or perfs are interesting but fall into the freaks category or even just bad printing.

Valuation of errors depends on how many exist and how much demand there is for the error. The market can be very volatile, with the first discovery of an imperf being sold for a lot and then with more being discovered eventually lowering the price tremendously. There are also stamps where this is some kind of error in the design, but since all issued stamps have the error and are not withdrawn, it is more of a curiosity with no premium value.  File:US 5c in 2c error.jpg|1917 US 5c value in 2c printing plate. File:Bahrain missing value.jpg|1952 Bahrain ½ anna with "½" missing. File:Philippines falls.jpg|1932 Philippines "Pagsanjan Falls", actually with an image of Vernal Falls in Yosemite Park in the US. Since much of the issue was withdrawn and high demand for the error, there is a more-than-expected premium for the stamp, never corrected. File:US honeybee error.jpg|US 25c honeybee, black lithography missing (but not black engraving). File:US 3c defense.jpg|US 3c Defense, imperf between. File:US Hammerskjold error.jpg|1962 Dag Hammerskjold, yellow printing inverted. While the first ones found were legitimate errors, even found on some FDCs, the post office department decided to print millions more of the error as an act of revenge. File:Cameroun inverted ovpt.jpg|1916 Cameroun, overprint inverted. File:Canal Zone missing ovpt.jpg|Canal Zone, left stamp missing overprint. It requires an attached overprint stamp to prove this error. 