HM Revenue and Customs gives us all 'allowances', which are deducted from our earnings before tax is calculated. Tax is only due on the balance.
The personal allowance for tax year 2017/18 is £11,500. This means that the first £11,500 of your taxable income is tax-free.
In general, you receive the personal allowance if you are resident in the UK or if you are a citizen of a European Economic Area (EEA) country (EU countries and also Iceland, Liechtenstein and Norway) or Switzerland. The level of the personal allowance is usually announced each year by the Chancellor as part of the autumn Budget.
These changes then take effect from the following 6 April. There are other tax-free allowances which can be claimed depending on your circumstances, such as Blind Person's Allowance, for example. See the GOV.UK website for more information on other allowances you may be eligible to claim for.