HMRC update the standard tax-free personal allowance every tax year. For the 2019/20 tax year, the standard tax-free personal allowance is £12,500 so most employees will end up with a tax code of 1250L. If you are puzzled by the numbers and letters in your tax code, below is a brief and simple guide to help you understand what your tax code means.
Broadly speaking, there are 2 types of tax code: cumulative and non-cumulative.
An example of a cumulative tax code is 1250L.
An example of a non-cumulative tax code is 1250L W1 or 1250L M1 or 1250L W1/M1 or 1250L X.
Cumulative tax codes calculate the tax due in the current pay period as the difference between the total tax due to date and the total tax paid up to the last pay period. As you will note from this, it is possible to get a negative difference if the total tax due to date is less than the total tax deducted up to the last pay period. This could be the case for example where an employee has received a bonus in the last pay period which results in more tax being deducted in that pay period than normal, or if an employee has had a gap in their employment. In this situation, the employee would receive a tax refund via payroll.
Non-cumulative tax codes are also known as Emergency Tax Codes. Non-cumulative tax codes calculate the tax to be deducted in each pay period by taking into account only the taxable earnings for that pay period.
The amount that an employee gets as their tax-free personal allowance is determined by the numbers that make up the tax code and also the letter that precedes or supersedes those numbers. If the tax code is made up of numbers followed by the letters L, M, N or T, multiplying the number by 10 will give you the total tax-free personal allowance for the tax year. Multiplying the tax code number by 10 and then dividing that by the number of pay periods (52 for weekly, 12 for monthly) will give you the tax-free personal allowance per pay period. HMRC will adjust the tax code to collect more tax by reducing the value of the tax-free personal allowance. If HMRC need to collect tax on things like Benefits in Kind and the value of these is such that they are more than the value of the tax-free personal allowance, they will issue a K tax code (tax code with a K prefix). This tax code has a negative tax-free personal allowance which means that tax is calculated on all earnings (no tax-free personal allowance) as well as an additional amount determined by the value shown after the letter K. Other common tax codes are BR (no tax free allowance and all income taxed at 20%), D0 (no tax free allowance and all income taxed at 40%) and 0T (no tax free allowance and all income taxed at 20% and 40% respectively in accordance with the relevant tax brackets).
What to do if you think your tax code is wrong
It is always a good idea to regularly check the tax code shown on your payslip. Remember, the lower the number shown before the letter in your tax code, the more tax you will pay. HMRC will issue revised tax codes from time to time and they are supposed to write to the employee to let them know that their tax code has been revised. At the same time, they will also issue a coding notice to the employer instructing them of the change. The coding notice that is issued to the employer will never tell the employer how the tax code has been worked out. If you think that your tax code is incorrect, you can use the HMRC Personal Tax Account service (https://www.gov.uk/check-income-tax-current-year). You will need to create an account first if this is your first time using the service. Alternatively, you can also contact HMRC on 0300 200 3300, making sure that you have your National Insurance number to hand.