There are a number of reasons why you might need to contact HMRC about changes in your income. 

HMRC’s guidance states that this could happen because you:

For example, reasons you may need to contact HMRC are if you are self-employed, a company director, have annual income over £100,000 and / or have undeclared income from savings, investment, property or overseas income. The £100,000 threshold for the Self-Assessment threshold for taxpayers taxed through PAYE only, has increased from £100,000 to £150,000 with effect from 6 April 2023. However, the Self-Assessment for 2022-23 tax returns remains at £100,000.  

Taxpayers that need to complete a Self-Assessment return for the first time should inform HMRC as soon as possible. The latest date that HMRC should be notified is by 5 October following the end of the tax year for which a Self-Assessment return needs to be filed. If you are required to submit a Self-Assessment return for 2022-23, you should ensure that you file your tax return electronically and pay any tax due by 31 January 2024.

HMRC has an online tool www.gov.uk/check-if-you-need-tax-return/ that can help you check if you are required to submit a Self-Assessment return.

There are two small exemptions from tax that may apply:

Where each respective allowance covers all the relevant income (before expenses) the income is tax-free and does not have to be declared.

If you have undeclared income, it is always preferable to contact HMRC as soon as possible. We would be happy to assist.

Source:HM Revenue & Customs| 03-07-2023