Q: What are "REVENUE" stamps?
A: Revenue stamps (sometimes also known as "fiscal" stamps) are/were issued by various countries, counties, cities & municipalities to pay for various taxes and fees. Putting a revenue stamp on the article, receipt or document indicated that the appropriate fees had been paid (or in some cases to indicate that the items was tax or duty-free).
Many people that collect postage stamps also collect revenue stamps. While many revenue stamps "look" like postage stamps, they are a totally separate category and generally have nothing to do with postage stamps as such (except in some countries, mostly British Colonies, where stamps did double-duty and they are marked "Postage & Revenue").
Collecting revenue stamps is a fun hobby. While the stamps themselves are interesting, I personally find that collecting them on the original document is far more interesting.
Here in the USA, revenue stamps have been issued by the federal governement, as well as the individual states, county & city governments for a large variety of reasons, some of which are listed below:
Many foreign countries have also issued revenue stamps. Most of these are "documentary" type of stamps and were affixed to various "documents", such as property deeds, bills-of-ladings, store receipts, etc. Currently, the most widely used revenue stamps are "airport tax" stamps. In many foreign countries, you have to pay a "departure tax", proof of which is a stamp (although sometimes just a plain receipt) that is attached to the back of your airplane boarding pass. This is a very popular way for smaller and poorer nations to earn income, especially those in the Caribbean & Africa. As time permits, I will post scans of these type of stamps on this site (http://revenuestamps.webs.com/images.htm). Technically, you pay a departure/airport tax here in the USA as well, but it is generally buried in your airfare fees and you do not get a separate stamp on your boarding pass.
If you travel enough, obtaining revenue stamps may be very easy (and at no extra cost to you). A few years ago, I was on the island of St. Kitts (Caribbean) and I purchased a postcard from a souvenir shop. The receipt that I was given had a 10c postage stamp on it to indicate that I paid some sort of tax on that card! In 1993 I was on the island of St. Vincent and purchased a bottle of beer at a grocery store; on the back of the receipt was a stamp affixed !
Additionally, I have created a 16-page sampler exhibit about worldwide revenue stamps that has been shown several times at the Mid-Cities Stamp Club EXPO, you can download the PDF file here.
St. Vincent bisected "3d." Revenue stamp
A partial listing of catalogs that listed revenue stamps is shown below: