When your income or tax circumstances change, HM Revenue and Customs (HMRC) may issue a new PAYE tax code so your employer or pension provider deducts a different amount of Income Tax. A pay rise does not automatically produce a new code: HMRC changes it when the information it holds means your tax-free amount or expected tax bill has changed. Employers and pension providers normally report job and pension details, while you must report some other taxable income yourself. Check HMRC’s Income Tax online service or app whenever a code looks unexpected.
What a tax code does
Your tax code is an instruction from HMRC to an employer or pension provider. It is used with each pay or pension payment to calculate how much Income Tax to deduct under PAYE. The numeric part represents the amount of income HMRC estimates can be paid tax-free after relevant adjustments. The letters describe aspects of your tax situation.
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HMRC can reduce the tax-free amount used in the calculation for items such as untaxed income, taxable benefits or tax that needs to be collected because too little was deducted earlier. It can also change the code when circumstances increase the amount of tax you are expected to pay. HMRC’s explanation is direct: “HM Revenue and Customs (HMRC) change your tax code if you need to pay a different amount of tax.”
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For HMRC’s 2026 guidance, the standard Personal Allowance is £12,570, although the allowance is not the same for everyone and can be affected by income and circumstances. The allowance and detailed code rules are tax-year-sensitive, so use the figures shown in your current HMRC record rather than relying on an old payslip.
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Changes that can make HMRC alter your code
HMRC recalculates your PAYE position from information supplied by employers, pension providers and you. A revised code is sent to the relevant payer when HMRC decides that a different amount should be deducted.
| Change | Who normally tells HMRC | Possible PAYE result | What you should do |
|---|---|---|---|
| Starting a job or changing employers | The new employer, using payroll information and your starter details | A normal cumulative code once records are matched, or a temporary emergency code if previous details are missing | Give the employer your P45, or complete its starter checklist if you do not have one |
| Higher or lower earnings from an existing job | Your employer reports changed pay information | HMRC may revise the estimate of tax due; a code change is not automatic for every pay rise | Check HMRC’s estimated income if the code or deductions do not make sense |
| An additional job or pension | The employer or pension provider | Each source generally receives its own code, with the available allowance allocated between sources | Confirm that every payer and the expected total income appear in your HMRC account |
| Taxable benefits, such as a company benefit | Usually the employer, with details also visible in your tax record | HMRC may reduce the tax-free amount to collect tax through payroll | Check the benefit value and tell HMRC if it is missing or wrong |
| Savings interest above your Personal Savings Allowance or other taxable income | You may need to report it, depending on the income and your circumstances | HMRC may adjust PAYE, request Self Assessment, or deal with the amount another way | Do not assume every type of income is settled through a PAYE code |
| Tax owed because an earlier code deducted too little | HMRC uses its records and previous-year calculations | Part of the amount may be collected through a future code | Review the calculation and contact HMRC if the underlying figures are wrong |
Will a pay rise change your tax code?
Not necessarily. Your employer reports the changed earnings, but HMRC changes the code only if the new information alters the amount of tax that should be collected through PAYE. If your tax-free allowance, benefits and other adjustments stay the same, your code may remain unchanged while the higher salary simply produces more tax under that code.
A code change is more likely when the higher earnings affect an HMRC estimate, move you into a different tax treatment, alter the value of an adjustment, or reveal that the existing code was based on outdated information. Conversely, a lower salary does not guarantee an immediate code change either. Payroll data must reach HMRC, be matched to the correct employment and feed into a revised calculation.
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Look at both the code and the tax deducted on your payslip. A different net pay amount alone does not prove that the code is wrong, and an unchanged code after a pay rise is not, by itself, an error.
What happens when you start or change a job?
Give the new employer the right starter information
- Give your new employer your P45 from the previous job as soon as you receive it.
- If you do not have a P45, complete the employer’s starter checklist accurately, including whether you have another job or pension.
- Check the first payslip for the tax code used and compare the employer shown in HMRC’s Income Tax service with your actual job.
The employer sends employment and pay details to HMRC. HMRC says new employment details should normally be available to view online within six weeks after the first payday. Its emergency-tax guidance also says that updating information after a job starts can take up to 35 days, so a new code may not appear immediately.
Why an emergency code appears
If the employer does not yet have previous-income details, payroll may use an emergency code. Common indicators are a code ending in W1 or M1, the letter X, or the marker NONCUM. These codes calculate tax using only the current week’s or month’s pay rather than your cumulative year-to-date income. That can temporarily deduct too much or too little tax.
An emergency code does not mean you have done anything wrong. It means the normal record has not yet been assembled. Supplying the P45 or starter information helps the records match. If the code is still unchanged after the relevant information should have arrived, use HMRC’s online record to check the job and estimated income.
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You have one Personal Allowance for a tax year, even if you have several employments or pensions. HMRC normally gives each income source its own tax code. One main job or pension may receive most or all of the allowance, while another source may use a rate code such as BR, D0 or D1. The correct allocation depends on your total income and circumstances; the examples and rates are tax-year-sensitive.
Do not assume the largest employer automatically has the right allocation. HMRC’s estimate of your combined income determines how the allowance and deductions should be spread. If you live or work under Scottish or Welsh tax arrangements, different rates or codes may apply.
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Check the record when a second source starts or ends
- Open the PAYE section of your Personal Tax Account or the HMRC app.
- Confirm that every current employer and pension provider is listed.
- Check that a former employer or pension has been removed or marked as ended.
- Review HMRC’s estimated income for each source and the total.
- Check where the Personal Allowance has been allocated and whether the split reflects your circumstances.
An old employer left on the record can cause HMRC to expect income you are no longer receiving. A missing second job can have the opposite effect. Correcting the list and estimates is more useful than trying to infer the answer from one payslip.
What if your income is not from employment?
Job and pension changes are generally reported by the payer. You must tell HMRC about certain other taxable income changes yourself. Examples include new income from self-employment or property, taxable benefits not correctly reflected by an employer, and other income HMRC specifies.
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsHMRC may respond in different ways. It could adjust a PAYE code, ask you to complete a Self Assessment return, or issue a refund where the records show that too much tax was paid. Not every amount is collected through payroll, so do not treat a new code as a complete calculation of all your tax obligations.
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When reporting non-PAYE income, keep the figures and dates that support the estimate HMRC uses. If the amount is seasonal, irregular or only a one-off, explain that rather than allowing a permanent annual estimate to be built from a single payment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to check and correct a tax code that looks wrong
- Sign in to HMRC’s “Check your Income Tax” service or use the HMRC app.
- Review the employers and pension providers shown on the record.
- Check HMRC’s estimated taxable income for each source and the total expected for the tax year.
- Check company benefits, other taxable income and expenses included in the calculation.
- Correct missing or inaccurate information through the service, or follow HMRC’s contact instructions if the service cannot change the item.
- Compare the revised code with the next payslip after HMRC has processed the change.
HMRC says it will notify you and the employer within 15 working days when the code needs changing. For a worker paid monthly, the revised code should appear on the next or following payslip. For a worker paid weekly, HMRC says it should appear by the third payslip after the change is issued.
If you have just started a job, HMRC advises allowing up to 35 days for the income details to arrive before contacting it when the online service cannot be used. That waiting period is specific to the new-job information flow; it is not a reason to ignore an obviously incorrect employer, benefit or income entry already visible in your account.
How to tell whether the result is an expected adjustment or an error
| What you see | Likely explanation | Next step |
|---|---|---|
| A new job uses W1, M1, X or NONCUM | Previous pay details have not yet reached or matched HMRC | Provide the P45 or starter checklist details and allow the stated processing time |
| The code changes after a benefit or other income is added | HMRC is collecting tax on an amount not covered by the tax-free allowance | Verify the amount and the tax year in the online record |
| A former employer remains listed | HMRC has not received or matched the leaving information | Update the employment record and check the next code |
| Two jobs both appear to grant the full allowance | The allowance allocation or employment records may be wrong | Review the PAYE section and ask HMRC to correct the allocation |
| The code is corrected but deductions change sharply | Earlier payslips may have deducted too much or too little | Check the cumulative calculation; a refund or further tax collection may follow |
A changed code alone does not prove that you overpaid or underpaid. An incorrect code can produce either result. Once HMRC corrects the record, an overpayment may be refunded or tax still owed may need to be collected.
A practical checklist after any income change
- Keep the P45, starter checklist information and first payslip when changing jobs.
- Record the date a job or pension started or ended.
- List every employment and pension, including small or temporary sources.
- Report new self-employment, property income and other taxable income when HMRC requires it.
- Check benefits, expenses and HMRC’s annual income estimate rather than looking only at the code letters.
- Recheck the record after HMRC’s stated processing window and after the revised code reaches payroll.
The useful question is not simply “Has my salary changed?” It is “Does HMRC now have different information about my expected taxable income or deductions?” If the answer is yes, a new code may follow; if not, the existing code can remain while the tax deducted changes with your pay.
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