Taxes on knowledge was a slogan defining an extended British campaign against duties and taxes on newspapers, their advertising content, and the paper they were printed on. The paper tax was early identified as an issue: "A tax upon Paper, is a tax upon Knowledge" is a saying attributed to Alexander Adam (1741–1809), a Scottish headmaster.
The "taxes on knowledge" were at their peak in 1815, as the Napoleonic Wars ended. The Liverpool administration actively discouraged certain sections of the press, with prosecutions, including those for seditious libel, aimed at editors and writers. The principle of taxing publications and pamphlets had been introduced by an Act of 1712, at the level of a halfpenny (½d.). The duty had risen over time to 4d.
The Newspaper and Stamp Duties Act of 1819 was not very effective in controlling the circulation of news, but cramped the development of newspapers. It was aimed at the journalism of William Cobbett, the Hunt brothers (The Examiner), and Thomas Jonathan Wooler (The Black Dwarf). From 1819, "newspaper" was defined carefully, and the fiscal burden fell on all periodicals that were more frequently published than monthly, and priced below 6d. It had a negative effect on the English provincial press, i.e. newspapers outside London; and drove out cheap political papers.
Stamp duty was levied on newspapers, and the first phase of the campaign was the distribution of newspapers that were unstamped, and therefore illegal. A central figure of this "war of the unstamped" was Henry Hetherington. His unstamped paper, The Poor Man's Guardian, was launched in 1831. It tested the boundaries of the government's willingness to enforce the duty, recruiting hundreds of paper sellers and flaunting its illegal status. The National Union of the Working Classes took up the attack on "taxes on knowledge"; it had an Owenite background, with the British Association for Promoting Co-operative Knowledge founded in 1829.