If your payslip suddenly looks slimmer and the letters 0T M1 are staring back at you, you’re not imagining things. This tax code often appears without warning and can quietly shave hundreds off your take-home pay.
The term here — tax code 0T M1 — isn’t just jargon. It usually means HMRC doesn’t have enough up-to-date information about your employment, so you’re being taxed with no personal allowance at all and only on a Month 1 basis. Translation? You could be paying more tax than necessary.
And yes, in many cases, it feels like an emergency code — even when no emergency happened.
This guide explains exactly what’s happening, why it occurs, and how to fix it without spiralling into HMRC phone-hold purgatory. You’ll also see real examples, common mistakes, and a practical framework to get your tax code corrected properly.
What Is Tax Code 0T M1?
Here’s a plain-English snapshot of what this code signals on your payslip. Tax code 0T M1 means you are not receiving any tax-free personal allowance, and your income is being taxed on a non-cumulative basis — as if each month is a fresh start.
Breakdown:
- 0T = Zero personal allowance applied
- M1 = Month 1 basis (each month taxed in isolation)
Instead of your income balancing across the tax year, each payslip is treated as if it’s your first one.
Is 0T M1 an Emergency Tax Code?
These are the typical situations where HMRC applies this code as a precaution. While not officially labelled an “emergency tax code,” it behaves exactly like one in practice.
HMRC applies 0T M1 when:
- You’ve started a new job without a P45
- Your employer hasn’t submitted updated records
- Your income situation looks unclear in HMRC’s system
- You have multiple income sources
- Your tax details haven’t synchronised correctly
The system defaults to “better safe than sorry” mode — and unfortunately, your payslip takes the hit.
Why Did I Get Put on 0T M1?
These are the most common real-world triggers behind this tax code.
- Starting a new job without submitting a P45
- Switching employers mid-tax year
- Incomplete starter checklist details
- Payroll errors from your employer
- HMRC system delays
- Multiple jobs or pensions
- Sudden salary increases
Even people who do everything right can still get caught. Sometimes it’s not you — it’s just the system misfiring.
How 0T M1 Impacts Your Pay (Real Example)
This comparison shows exactly how much income you can lose. Suppose you earns £3,000 per month gross:
| Scenario | Tax Deducted | Take-Home Pay |
| Normal code (1257L) | ~£430 | £1,970 |
| 0T M1 | ~£670 | £1,730 |
That’s about £240 less every month — without any lifestyle change. Over three months, that’s £720 tied up unnecessarily.
The PAYSLIP RESET METHOD: How to Fix Tax Code 0T M1
Follow this proven framework to efficiently correct your code.
Step 1: Check Your Personal Tax Account
- Review employment details
- Check income records
- Confirm current tax code
Step 2: Confirm Your Employment Info
Ensure HMRC has:
- Correct employer name
- Accurate start date
- Realistic salary estimate
Step 3: Submit HMRC Update
Update incorrect information or request a tax code review.
Step 4: Contact Your Employer
Ask payroll whether the correct RTI (Real Time Information) was submitted.
Step 5: Track Progress
HMRC typically processes updates in 5–10 working days (as of 2025).
How Long Does It Take to Fix 0T M1?
Most taxpayers experience the following timeline:
- Online update tracked: 2–5 days
- Code adjustment issued: 5–10 working days
- Payslip correction visible: on the next pay cycle
Refunds may follow automatically — but always verify.
Can I Claim a Refund on 0T M1?
These are typical ways HMRC returns overpaid tax:
- Via adjusted future payslips
- Direct bank repayment
- End-of-year reconciliation
If the error lasted several months, the refund could be significant.
Comparison: 0T M1 vs Other Common Codes
Use this table to understand where 0T M1 ranks in severity.
| Code | Meaning | Typical Impact |
| 1257L | Standard allowance: personal allowance of £12,570 per year (2025/26) | Normal tax with allowance applied |
| BR | All income is taxed at the basic rate | Moderate tax |
| D0 | All income is taxed at a higher rate | High tax |
| 0T M1 | No allowance + monthly reset | Very high tax / possible overpayment |
For 2025/26, the standard personal allowance (if code 1257L or similar applies) is £12,570 per year.
0T M1 removes that allowance entirely — which is why the impact is so steep.
Common Mistakes People Make
- These habits quietly delay refunds and increase losses.
- Ignoring that 0T M1 appeared
- Assuming HMRC automatically fixes code errors
- Not reviewing payslips regularly
- Misplacing P45 or P60 documentation
- Leaving everything to payroll
Big myth: “It’ll sort itself out.”
Often, it won’t — unless you intervene.
2025 Updates You Should Know
- These changes affect how tax codes are processed this year.
- HMRC now prioritises online updates over paperwork. UK+1
- RTI reporting errors remain a major cause of incorrect codes.
- Temporary codes like 0T M1 can linger longer if employer data remains delayed.
How to Change 0T Tax Code Quickly
Here’s the fastest route in 2025:
- Log in to your HMRC Personal Tax Account
- Update your employment info
- Request a tax code review
- Screenshot confirmation for your records
- Follow up after 7 days if there’s no change
HMRC Contact Info (Secondary Option)
If you prefer to speak to someone directly, you can call HMRC’s Income Tax helpline: 0300 200 3300 (UK) or +44 135 535 9022 (from outside the UK).
Note: phone lines can be busy; online contact or the personal tax account is usually faster and more reliable.
| Expert Tip: One small habit can save hundreds per year. Check your tax code every month — like you check your bank balance. It’s dull, but it pays off. |
FAQs
Q. What does tax code 0T M1 mean in simple terms?
Tax code 0T M1 means you are not receiving any tax-free personal allowance, and all your income is taxed each month separately, often because HMRC lacks updated employment details.
Q. Why did my tax code change to 0T M1?
Your tax code may be set to 0T M1 if you start a new job without a P45, change employers, have multiple income sources, or HMRC receives incomplete or delayed payroll data.
Q. Is 0T M1 worse than the emergency tax?
Yes. 0T M1 removes your personal allowance entirely and can result in significantly higher tax deductions than standard emergency-tax codes.
Q. How do I fix tax code 0T M1 fast?
Log in to your HMRC Personal Tax Account, correct your employment information, and request a tax code review. Most corrections reflect within one pay cycle.
Q. Will I get a refund for 0T M1 overpayment?
Yes. If you were overtaxed under 0T M1, HMRC typically refunds the excess through revised payslips or direct bank payment after code correction.
Q. How long should 0T M1 remain on my payslip?
It should be temporary. If it remains after one pay cycle, you should take action to request a correction.
Q. Does 0T M1 affect future tax years?
No. It only affects the current tax period and does not permanently change your tax status once corrected.
Q. Is 0T M1 common for second jobs?
Yes. HMRC may apply this code if your personal allowance is already assigned to another income source or if details for the second job are missing.
Final Thoughts
The tax code 0T M1 can feel like a silent tax ambush — confusing, frustrating, and unfair. But it’s not permanent, and it’s usually not personal. It’s just a data mismatch.
The cure?
Awareness. Action. Consistency.
Check your details. Update your records. Monitor your payslips. And follow up when needed.
Because every pound you earn should land exactly where it belongs — with you.
Related: M1 Tax Code Explained: What It Means and How to Fix It (2025 Guide)
