When America was still a colony under the control of Great Britain, the phrase "No Taxation Without Representation" became a rallying cry for those in America who felt that they were not being granted the appropriate rights of representation granted to other Englishmen. Colonists felt they were being taxed by Parliament even though the colonies were not represented there, meaning they were being taxed without being represented; they deemed this tyrannical, and taxation without representation became one of the central causes of the American Revolution.
While the phrase Taxation Without Representation has subsequently been used around the world and applied to countless situations, the phrase was originally used and became ubiquitous in the colonial days of the United States, sometime around 1750. It became a common rallying cry throughout the colonies, and prominent figures began using the slogan in speeches and campaigns to gain support for their cause. The contention of such figures was that laws applying only to the colony were illegal because the colonists' rights as Englishmen were essentially being denied. If the colonies could be taxed without representatives from those colonies taking part in Parliament, then other laws could similarly be enacted, which was a violation of rights.
The trouble with taxation without representation stemmed from the fact that Parliament was on the other side of the Atlantic Ocean. The colonies in America were very remote, making actual representation difficult. Some critics against the No Taxation movement argued that the colonists received virtual representation, which implied that parliament had the right to make laws for the colonies as it deemed fit. This was later made law by parliament.
Perhaps one of the most famous instances of direct rally against taxation without representation was the Boston Tea Party. After the Tea Act, which imposed a tax on tea, among other things, the colonists demanded its officials to return a ship carrying tea back to Britain. When the officials refused, colonists boarded the ship and destroyed the tea, dumping it into Boston Harbor. The American Revolution began only a few years later as fervor against such taxation grew.
In more recent times, the phrase has been used for other applications. it appeared on license plates in Washington, D.C., as part of a campaign to grant voting rights to citizens living in the district. it has also been used as a rallying cry for groups in the U.S. who believe citizens are being overly taxed by the government.