HMRC ‘PAYE Coding Notice’ (P2) 2026: 7 Reasons Your Tax Code Changes + What Decides Refund vs Underpayment
Your tax code can change even if your salary hasn’t. HMRC updates PAYE tax codes when your income, benefits, allowances, or estimated tax position changes. When that happens, you may get a PAYE Coding Notice (form P2) showing how HMRC built your code and what it means for your next payslip.
This guide explains the 7 most common triggers in 2026, what to check on your P2, and the practical rule that decides whether you’re heading toward a refund or a tax bill (underpayment).
45-second summary (busy people)
- P2 (PAYE Coding Notice) tells you your tax code and how HMRC calculated it.
- HMRC changes your tax code when you need to pay a different amount of tax (usually after a change in income/circumstances).
- You can check your current tax code on your payslip, in the HMRC app, or via your online tax account (and opt into paperless notifications).
- If your code is wrong, HMRC says they’ll update it and notify you and your employer (typically within 15 working days once you report changes).
- Refund vs underpayment: if your code gives you too much tax-free pay, you’ll likely underpay; if it gives you too little, you may overpay and later get refunded.
What is an HMRC P2 (PAYE Coding Notice)?
A P2 is HMRC’s “notice of coding” that shows your PAYE tax code and the allowances and deductions HMRC used to create it. HMRC’s PAYE guidance explains that P2 notes are generated based on the allowances/deductions within your code and help explain how it was built.
Where to find your tax code (even if you don’t receive a paper letter)
- Online: check your tax code in your HMRC online account (Personal Tax Account).
- HMRC app: view your current code and changes.
- Payslip / P60: your employer’s payroll uses the code HMRC issues.
- P2 letter: if HMRC sends one (or if you’ve opted for paperless notifications).
The 7 most common reasons your tax code changes (P2 triggers) in 2026
HMRC says tax codes change when you need to pay a different amount of tax—usually after a change in income or circumstances. Here are the 7 triggers that show up most often on real P2 notices (and the quick check that catches errors fast).
1) You started a new job or changed employer (missing starter info)
If HMRC or your employer doesn’t have complete starter details, you can be placed on an emergency-style basis (for example BR or 0T), which changes how tax is deducted. This often fixes itself once HMRC receives full pay and starter information—unless your details are wrong.
2) You now have two jobs (or a job + pension)
Most people should only have the main personal allowance applied once. When you add a second PAYE source, HMRC may move allowance to one job and apply basic rate/no allowance elsewhere, changing both payslips.
3) Your taxable benefits changed (company car, medical cover, etc.)
Benefits-in-kind are often collected through your tax code. HMRC provides a specific route to update or correct company benefits if you think your code is wrong.
4) You started receiving the State Pension (or another taxable state benefit)
Some income is paid without PAYE being deducted at source. HMRC may adjust your code so the tax is collected through your employment/pension PAYE instead.
5) HMRC is “coding out” an earlier underpayment
If you underpaid tax in a previous year (often found after end-of-year checks), HMRC may adjust your code to collect that amount gradually through PAYE rather than a separate payment.
6) Your tax reliefs/expenses changed (work expenses, professional fees, etc.)
Reliefs (like eligible work expenses) can increase the tax-free amount in your code. If the relief is wrong or out of date, it can swing your PAYE deductions noticeably.
7) Marriage Allowance transfer (M / N codes) or allowance adjustments
Marriage Allowance can shift a portion of allowance between spouses/civil partners and is reflected in tax codes. If it’s applied to the wrong person or year, your PAYE can be off.
Refund vs underpayment: the simple rule that decides which way it goes
Your PAYE deductions are essentially driven by one thing: how much tax-free pay your code gives you versus what you actually should receive.
| If your code… |
What happens during the year |
Likely outcome |
Fast check on your P2 |
| Gives too much tax-free pay (allowances too high or deductions missing) |
You pay too little tax via PAYE |
Underpayment later (often corrected by a code change or end-of-year calculation) |
Are benefits/pension/second job income missing from the “deductions” section? |
| Gives too little tax-free pay (allowances too low or deductions too high) |
You pay too much tax via PAYE |
Refund (often automatic, depending on your situation) |
Is HMRC estimating income too high, or coding out a debt you already paid? |
What to check on your P2 (10-minute checklist)
- Name, address, National Insurance number (basic but common mismatch).
- Employer/pension payer listed on the notice (make sure it’s the right one).
- Benefits: company car, medical insurance, etc. (are they current?).
- State Pension or other taxable income included (if relevant).
- Underpayment being collected: is it yours, and is the amount reasonable?
- Reliefs: job expenses/professional fees—still valid for 2026?
- Marriage Allowance indicator (M/N) if you claimed it.
- Timing: if you reported a change, HMRC says they normally update your code and notify you/your employer within 15 working days.
If your tax code is wrong: the safest way to fix it (HMRC-approved)
Start with HMRC’s official tax code pages. HMRC explains you can check your tax code online (or in the HMRC app) and report changes. If your tax code needs to change, HMRC says they will update it and tell you and your employer—typically within 15 working days after you report changes.
Step-by-step fix
- Check your tax code online (Personal Tax Account) or in the HMRC app.
- Use HMRC’s “update your tax code” process if your job, income, or benefits changed.
- If the issue is company benefits, HMRC provides a dedicated guidance page to update benefit details.
- If you still can’t correct it online, contact HMRC (Income Tax helpline is commonly used for PAYE code issues).
Common P2 mistakes that cost you money (avoid these)
- Not noticing paperless notifications: you can opt in so HMRC emails you when the code changes.
- Old benefits still in the code: a company car returned months ago still reducing your tax-free pay.
- Second job not shown: allowance applied twice, then you underpay and get hit later.
- Coding out already-paid tax: underpayment collected again because HMRC hasn’t matched the payment.
FAQ
Do I always get a P2 letter when my tax code changes?
Not always as a paper letter. HMRC explains you can find your code online or in the HMRC app, and you can sign up for paperless notifications so HMRC emails you when your code changes.
How quickly will my new tax code show on my payslip?
HMRC says after they update your code, they will tell you and your employer within 15 working days. For monthly pay, it should appear on your next or following payslip; for weekly pay, typically by your third payslip after the change.
What should I do the moment I receive a P2?
Check the allowances/deductions list line-by-line and confirm anything that changed recently (job, benefits, pension, expenses). If something is wrong, use HMRC’s official “update your tax code” process.
Is my employer allowed to change my tax code for me?
Employers use the tax code HMRC issues. If it’s wrong, you generally need HMRC to correct it and notify your employer via payroll updates.
Will an incorrect tax code automatically lead to a refund?
Not always. If the code causes you to overpay, you may receive a refund, but the timing depends on your circumstances and HMRC’s reconciliation. The key is to fix the code early to prevent large over/underpayments building up.
Next reads (internal links you can publish)
- HMRC Tax Code Changed to 1257L: What It Really Means + When It’s Still Wrong (2026)
- HMRC Letter After PAYE Error: Who Pays the Difference — and What Happens If You Ignore It (2026)
- P800 Tax Calculation Explained: Why HMRC Says You Owe Money (and When You Get a Refund) (2026)
Important note
This article is general information (not tax advice). PAYE codes depend on your specific income sources and benefits. If your P2 shows something you don’t recognise (or your payslip deductions suddenly jump), use HMRC’s official tools or seek professional advice.
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