In the UK tax system, personal allowance is the threshold above which income tax is levied on an individual's income. A person who receives less than their own personal allowance in taxable income (such as earnings and some benefits) in a given tax year does not pay income tax; otherwise, tax must be paid according to how much is earned above this level. Certain residents are entitled to a larger personal allowance than others. Such groups include: the over-65s (followed by a further increased allowance for over-75s), blind people, and married couples where at least one person in the marriage (or civil partnership) was born before 6 April 1935. People earning over £100,000 a year have a smaller personal allowance. For every £2 earned above £100,000, £1 of the personal allowance is lost; meaning that incomes high enough will not have a personal allowance.

On 22 April 2009, the then Chancellor Alistair Darling announced in the 2009 Budget statement that starting in April 2010, those with annual incomes over £100,000 would see their Personal allowance reduced by £1 for every £2 earned over £100,000, until the Personal allowance was reduced to zero, which (in 2010–11) would occur at an income of £112,950.

For every additional £100 earned, the Personal allowance was reduced by £50, meaning that an additional £50 would be taxed at the marginal rate (40%), resulting an additional tax liability of £20, resulting in an effective additional 20% marginal taxation over and above the 40% tax already due.

This resulted in an anomalous effective 60% marginal tax rate in the income band between £100,000 and £112,950, with the marginal tax rate returning to 40% above £112,950. As the Personal allowance has grown over the years, this has resulted in a corresponding increase in the size of the effective marginal 60% tax band. As of 2022–23, the effective 60% marginal tax rate now arises for incomes between £100,000 and £125,140.

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On 22 June 2010, the new Chancellor George Osborne, as part of the coalition deal which sought to increase the Personal Allowance to £10,000 from April 2015 as per Lib Dem policy,^[1] made the first increase of £1,000, making it £7,475 for the 2011-12 tax year.^[2] During the 2011 Budget, the allowance was raised by £630 to £8,105 from April 2012.^{[citation needed]} In 2013, George Osborne revised the plans to increase the Personal Allowance and bring forward the date at which it would reach the £10,000 target. This resulted in the allowance being raised to £9,440 from April 2013, before being increased to £10,000 from April 2014, a year earlier than originally planned.^[3][4][5] All these increases in the personal allowance came from rises in the personal tax.^[5][3] In 2016, Osborne determined that the tax increases no longer applied for personal allowance and decided to cut taxes personal taxes £1,000 less than the 2011 level when he increased the personal allowance to £11,500.^[6]

Married Man's allowance was the allowance for a legally married couple. The allowance was given at the man's highest rate of tax. During the early-1990s, then-Chancellor of the Exchequer, Norman Lamont overhauled the allowance and introduced the 10% allowance,^{[clarification needed]} which meant that all men had the same amount of money in their pocket,^{[clarification needed]} irrespective of highest tax rate. The allowance was scrapped from April 2000, first being announced in then-Chancellor Gordon Brown's 1999 budget,^[7][8] with the exception of people married, or in civil partnerships (introduced in 2005) where one spouse was born before 6 April 1935.

• Income tax in Scotland
• Welsh Rates of Income Tax