# Why Has My Tax Code Changed to BR or 0T? Your tax code can change to BR or 0T if HMRC lacks key payroll data or has allocated your personal allowance to another job. Learn why this happens and how to fix it. **Published:** 2026-07-06 **Updated:** 2026-07-06 **Source:** https://aztajournal.com/gb/why-tax-code-changed-br-0t --- > Your tax code has likely changed to BR or 0T because His Majesty's Revenue and Customs (HMRC) lacks key administrative information or has allocated your standard personal allowance to another income stream. These emergency or secondary codes remove your tax-free allowance from that specific job, temporarily increasing your tax bill. Your tax code changes to **BR** or **0T** when HMRC instructs your employer to deduct tax from every pound you earn without applying a tax-free personal allowance. This typically occurs because you have started a new job without providing key payroll documentation, or you have taken on an additional source of income. ## Key Takeaways: Why Your Tax Code Has Changed - **BR** stands for Basic Rate, which taxes all income from that specific source at 20% flat. - **0T** means you receive zero personal allowance, and your earnings are taxed across the basic, higher, and additional-rate bands. - **Missing documentation**, such as a P45 or a completed Starter Checklist, is the most common trigger for these tax code updates. - **Multiple income sources**, such as having a second job or a new pension, will prompt HMRC to apply these codes to your secondary income. - **These codes are temporary** measures that can be resolved once HMRC receives your correct details and payroll information. ## Why Has My Tax Code Changed to BR or 0T? A shift to a BR or 0T code means your £12,570 tax-free personal allowance has been completely removed from that specific pay packet. When your employer does not hold your historic income data or when you already claim your allowance elsewhere, HMRC implements these codes to prevent underpaying your income tax. | Tax Code | Tax Rate Applied | Personal Allowance | Common Reason for Use | | --- | --- | --- | --- | | BR | Flat 20% basic rate | None (allocated to another job) | Second jobs or second pensions. | | 0T | Progressive (20%, 40%, 45%) | None (withdrawn or unknown) | Missing P45, casual work, or high earnings. | ## Why Has My Tax Code Changed to BR? The BR tax code is used when HMRC allocates your entire tax-free personal allowance to a main job and taxes a secondary pension or second job at 20% on all earnings. Under this code, you do not benefit from any tax-free threshold on this specific source of income. 1. **You have taken on a second job:** HMRC assumes your primary employer already utilizes your £12,570 allowance, so your secondary earnings are taxed entirely at the basic rate. 2. **You have started drawing a second pension:** Similar to secondary employment, your pension provider is instructed to tax this ongoing income at a flat 20%. 3. **Direct instruction from HMRC:** Your employer has received a specific BR tax notice from the tax office for other administrative or coding reasons. ### Why Has My Tax Code Changed from 1257L to BR? Moving from the standard 1257L code to BR signifies that your £12,570 personal allowance is no longer being applied to this specific pay packet. This transition occurs if you start a new role and HMRC incorrectly designates your original job as your primary income source. When a direct HMRC instruction shifts your code from 1257L to BR, it is often because HMRC has reassigned your personal allowance elsewhere. If you only have one job, this code is incorrect and will lead to an immediate 20% deduction on your entire salary until resolved. ## Why Has My Tax Code Changed to 0T? The 0T tax code is applied when you receive no personal allowance and your earnings are taxed progressively up to 45% because your employer lack your financial history. Unlike a BR code, 0T can push your earnings into the higher and additional tax brackets depending on how much you earn in a pay period. 1. **Missing P45 or Starter Checklist:** Your new employer lacks the necessary tax information to assign a standard code, so they default to 0T under official pay-as-you-earn instructions. 2. **Your annual income exceeds £125,140:** Under the Income Tax Act 2007 (section 35), your personal allowance is reduced by £1 for every £2 earned over £100,000, meaning it is fully lost at £125,140. 3. **Payments received after leaving a job:** Your former employer is legally required to use a non-cumulative 0T code on any salary or bonus paid after you leave the company. 4. **Starting a pension without a P45:** Your pension provider has not yet received a tax code from HMRC and must default to 0T to prevent underpayment of tax. 5. **Casual work status:** The employer does not have your historical tax information or any starting declaration, triggering an automatic 0T code. ## Why Has My Tax Code Changed When Nothing Has Changed? Your tax code can change unexpectedly due to automatic HMRC administrative adjustments or because an employer failed to process your starter documents in time. When HMRC recalculates your estimated annual earnings, they may update your code to reclaim past unpaid tax, even if your daily job remains exactly the same. In other instances, an employer may have misplaced your P45 during an internal payroll transition, leading to an automatic emergency code like 0T. Checking your payslip regularly helps ensure that administrative errors are caught before they impact your net monthly take-home pay. ## How to Correct Your Tax Code with HMRC Correcting a BR or 0T tax code requires providing HMRC with your updated income details or submitting missing payroll documentation directly to your employer. Your employer cannot change your tax code on their own initiative; they must wait for official instruction from HMRC. 1. **Submit your starter paperwork:** Ensure your employer has received either your P45 from your previous job or a completed Starter Checklist. 2. **Check your Personal Tax Account:** Log in to the official GOV.UK portal to view your currently registered jobs, pensions, and assigned tax codes. 3. **Contact HMRC directly:** Call the official helpline on 0300 200 3300 to explain your employment situation and request a code adjustment. 4. **Submit a repayment claim:** If you have overpaid income tax on a BR or 0T code, ask HMRC to issue a tax code notice to refund the overpayment in your next payroll. ### Why has my tax code suddenly changed? A sudden change in your tax code is usually triggered by a change in your employment status, such as taking a second job, starting a pension, or starting a new role without submitting a P45. It can also happen if HMRC adjusts your record to collect unpaid tax from a prior year. ### Why has my tax code changed to 1257L? A change to the standard 1257L tax code means you have been granted the standard tax-free personal allowance of £12,570. This transition occurs once your employer has received your official tax details and HMRC confirms you are entitled to the standard allowance. ### What is the difference between BR and 0T tax codes? The BR code taxes all of your income at a flat basic rate of 20%, whereas the 0T code does not give you any personal allowance and taxes your income across multiple tax bands (20%, 40%, and 45%) depending on your level of earnings. ### Does my employer have the power to change my tax code? No, your employer does not have the legal authority to change your tax code on their own. They can only apply tax codes that are officially issued to them by HMRC, or use standard emergency default codes when you start working without a P45. ### How long does HMRC take to refund overpaid tax on a BR or 0T code? Once HMRC updates your tax code and sends the instruction to your employer, any overpaid tax is typically refunded automatically in your next scheduled payroll. If the tax year has already ended, HMRC will issue a P800 tax calculation and refund the money within a few weeks.