Your tax code tells your employer how much of your earnings should go to Her Majesty’s Revenue and Customs (HMRC) as tax. If you suspect there is a mistake in your tax code, it’s important to get in touch with HMRC as soon as possible because you could be paying tax at the wrong rate. Certain changes of circumstance, such as a change in your employment status, will alter your tax code, but HMRC cannot change the code without notifying you first.
Check which tax code you are currently on. The information is included on the PAYE Coding Notice sent to all working people by HMRC at the beginning of each financial year, and also on the P45 you receive when you stop working for an employer. The code can take different forms, but is usually a combination of letters and numbers. For example, the most common code for the 2011 to 2012 financial year is 747L, the basic personal allowance.
Check you know your National Insurance number. This is a nine-character combination of letters and numbers, with two letters followed by three pairs of numbers and finished with a single letter. The number is unique to you and identifies your information in the HMRC database.
Contact HMRC by telephone on 0845 300 0627, or by post at the address provided on the most recent tax-related communication you have received. You cannot contact HMRC by email for anything other than notifying a change of name or address.
Provide all the information HMRC staff ask for. They will ask for both your National Insurance number – to identify you in the HMRC system – and for your current tax code. Staff may also ask for further details about your employment. Once your tax code is confirmed, ask for written confirmation to be sent out to you by post and keep the notification in a safe place.
Keep HMRC informed of any changes in your life that might affect your tax code. This includes events like getting a second job or a change in the level of untaxed income you receive, for example, from a pension.