If you think your tax code is wrong you can tell HMRC about many changes using the check your income tax online service.
This service is part of your personal tax account so you’ll need to sign in with a government Gateway user ID and password.
If you don’t already have these you can create them.
In most cases HMRC will automatically update your tax code when your income changes – that’s because HMRC usually gets this information from your employer so if you’ve recently changed jobs or your pension has changed please allow 35 days for your details to update, before using the service.
On the personal tax account home page, select pay as you earn also known as PAYE to go to your PAYE income tax overview page, choose check current tax year and you’ll see your PAYE income tax summary for the current year from this page you can add missing info.
If you need to update your employment details, choose view or update employment details.
On this page you can update your estimated taxable income for the year & you can also add missing Company benefits including company cars.
After you report a change HMRC will contact you & if your tax code changes they will send you a new tax code notice. HMRC will also tell your employer or pension provider that your tax code has changed so you should see the new tax code on your next payslip and your employer will make any adjustments to your pay.