0T Tax Code: Every Pound You Earn Taxed From Day One

The number on your payslip is four characters long, starts with a zero, and it is costing you hundreds of pounds. If your tax code reads 0T, HMRC is taxing every single penny of your wages as though your £12,570 personal allowance does not exist.

That is not a rounding error. That is a structural decision baked into the PAYE system, and unless you act, it will keep happening every payday.

Why Your Payslip Shows 0T and Not 1257L

Your standard tax code, assuming you are a basic-rate taxpayer with no complications, should be 1257L. That code tells your employer to leave your first £12,570 tax-free and only start deducting from the remainder.

The 0T code is what happens when that information pipeline breaks down. HMRC instructs your employer to use 0T in a handful of specific situations:

• You have started a new job and your employer does not yet hold a P45 from your previous employer, or your P45 was lost or delayed
• You have more than one job and HMRC has already allocated your personal allowance to your primary employer
• Your personal allowance has been used up by another income source, such as a pension, benefit-in-kind, or investment income
• HMRC has received no starter checklist (the form that replaced the P46) from your new employer
• Your tax code was reset at the start of a new tax year before HMRC updated its records
• An administrative error somewhere in the chain caused HMRC to lose visibility of your circumstances

Notice what most of those have in common: they are caused by information failures, not by anything you did wrong. The frustration is entirely legitimate.

What 0T Actually Costs You on a Real Salary

Abstract tax code explanations are easy to skim past. So here is what 0T means in hard cash.

Suppose you earn £35,000 a year. Under your correct 1257L code, your taxable income is £35,000 minus £12,570, giving £22,430 liable to 20% basic rate tax. Your annual tax bill: approximately £4,486.

Under 0T, your employer taxes the entire £35,000. At 20% on the first £37,700 band, that is a bill of £7,000. You are overpaying by roughly £2,514 every year, or £209.50 every month.

For a higher-rate taxpayer earning £60,000, the maths is worse. Under 1257L, you pay basic rate on income up to £50,270 and higher rate on the rest. Under 0T, every pound from the first is taxed, pushing more of your income into the 40% band. The overpayment can reach £3,000 or more annually.

That is not theoretical. That money leaves your bank account on payday and sits with HMRC until someone corrects the record.

The Difference Between 0T and BR: Why It Matters

If you have ever seen the code BR on a payslip, you might wonder how it differs from 0T. Both are emergency-style codes, and both strip your personal allowance. The distinction is in how tax is applied:

• BR applies a flat 20% basic rate to all income, regardless of how much you earn. It is typically used for second jobs or pensions where HMRC knows the personal allowance has been claimed elsewhere.
• 0T applies the full banded rate structure: 20% up to £37,700, then 40% on income above that, then 45% above £125,140. If you earn enough, 0T will cost you considerably more than BR.

For a full breakdown of how these letters interact with your take-home pay, see Tax Code on Your Payslip: What Each Part Actually Means.

The "W1" or "M1" Suffix: Making 0T Even More Complicated

Your payslip might not just say 0T. It might say 0T W1 or 0T M1. These suffixes stand for Week 1 and Month 1 basis, and they change how your employer calculates tax each pay period.

Normally, PAYE operates on a cumulative basis. Your employer looks at your total earnings for the year to date and calculates whether you have paid enough tax overall. If you overpaid last month, this month's calculation adjusts accordingly.

With a W1 or M1 suffix, that cumulative logic is switched off. Each pay period is treated in complete isolation. This week's wage is taxed as though it were your entire year's income condensed into one period. There is no automatic correction for previous overpayments.

This matters enormously if you started a new job mid-year having already paid the right amount of tax at a previous employer. Without cumulative calculation, your new employer cannot see those earlier payments and cannot offset them. The overpayment simply accumulates.

HMRC adds the W1/M1 marker when it wants your employer to avoid making cumulative adjustments until the code situation is properly resolved. It is a holding mechanism, not a permanent state. But it does mean the automatic corrections you might hope for simply will not happen on their own.

Scenarios Where 0T Is Actually Correct

Before you ring HMRC in a fury, it is worth confirming whether 0T might be appropriate in your specific case.

Multiple jobs: If you have two or three sources of PAYE income, HMRC can only allocate your personal allowance once. Your primary employer gets 1257L (or something close to it). Every other employer should receive a code reflecting zero personal allowance, because it has already been used. If 0T appears on your secondary payslip, it may be entirely intentional.

Income above £125,140: At this level, your personal allowance is withdrawn entirely. HMRC codes you on 0T because there genuinely is no allowance to apply. If this is your situation, 0T is not an error.

An unresolved tax debt: In rare cases, HMRC may use 0T alongside a K code adjustment to recover an existing liability. K Tax Code Meaning: Why HMRC Is Adding to Your Bill explains that mechanism in detail.

If none of those apply to you, your 0T code is almost certainly wrong.

How to Fix a 0T Tax Code: The Shortest Route

The most important thing to understand: you do not have to wait for HMRC to notice. The system will not automatically correct a 0T code just because time passes. You need to initiate the fix.

Step one: Check your current code right now. You can check your tax code for free at /check-my-tax-code to confirm what HMRC currently holds on record and whether it matches what your employer is using.

Step two: Log into your Personal Tax Account at gov.uk. Navigate to the PAYE Income Tax section. You can see your coding notice here and, in many cases, update your details directly online without speaking to anyone.

Step three: Contact HMRC if the online update is not available. Call 0300 200 3300 (have your National Insurance number and employer's PAYE reference to hand). Explain that you have been placed on a 0T code and provide your employment details. HMRC will issue a new coding notice to your employer, typically within a few weeks.

Step four: Give your employer the P45 or starter checklist. If the 0T code arose because your employer lacked information, submit a completed starter checklist immediately. This alone may be enough to trigger a corrected code without HMRC involvement.

Step five: Track the correction. Once HMRC issues the updated code, your employer should apply it in the next payroll run. The cumulative PAYE system will then begin recovering your overpayment automatically across the remaining pay periods in the tax year.

For a more detailed walkthrough of disputing any incorrect code, Tax Code Incorrect: The Exact Steps to Fix It Fast covers the process step by step.

What Happens to the Tax You Have Already Overpaid

Good news: the money is not gone. HMRC operates PAYE on a cumulative basis, so once your correct code is reinstated, your employer will automatically underpay your tax in subsequent months to compensate. If you overpaid £400 in the first two months of employment, your employer's payroll software will spread that recovery across the months remaining in the tax year, reducing your deductions slightly each time.

If the tax year ends before the overpayment is fully recovered through payroll, HMRC will identify the shortfall during its end-of-year reconciliation (usually between June and November following the April year-end) and issue a P800 tax calculation. That letter will confirm you are owed a refund and explain how to claim it.

Do not wait for the P800 if you know you have overpaid. You can contact HMRC directly to request a repayment once the correct code is in place. Claim Back Overpaid Tax: Why HMRC Won't Chase You explains exactly why proactive claiming is always faster than waiting.

If Your New Job Triggered the 0T Code

Starting a new job is by far the most common trigger. The sequence usually goes like this: you leave an employer in, say, October. You start a new role in November. Your old employer issues a P45 but it gets delayed, lost in the post, or simply not handed over before your first payroll run. With no P45 and no starter checklist on file, your new employer is legally required to use an emergency code, and 0T is what HMRC defaults to.

The fix is simple in theory: get your P45 to your new employer as quickly as possible. If the P45 is lost beyond recovery, your new employer can use the information from a completed starter checklist (available on gov.uk) instead. Either document gives payroll the information needed to request the correct code from HMRC.

What you should not do is assume the problem will resolve itself by the next pay cycle. Payroll departments process hundreds of employees. Your emergency code will stay in place until someone physically updates the record.

The Second Job Problem: When 0T Is Partly Right and Partly Wrong

If you have a second or third PAYE job, your situation is more nuanced. Your personal allowance should be assigned to whichever job pays you the most (your primary employment). All other employers should typically use either BR or 0T, since the allowance is already allocated.

But here is where errors creep in. HMRC sometimes allocates 0T with the W1/M1 suffix to a second job rather than the cleaner BR code, which can mean slightly different tax outcomes depending on your earnings. And if HMRC has incorrectly identified which of your jobs is the primary one, your main salary could end up coded at 0T while your side income gets the personal allowance instead.

This is worth checking carefully. Log into your Personal Tax Account and confirm which employer HMRC has recorded as your main income source. If it is wrong, correct it online or call to update the record. The downstream effect on your monthly take-home can be significant.

You can run the numbers yourself using the salary tax calculator to compare what you should be paying against what is currently being deducted.

People also ask

How long does a 0T tax code last?

Can I ask my employer to change my 0T code themselves?

Will HMRC automatically refund tax paid under a 0T code?

Is 0T the same as an emergency tax code?

The Hidden Risk: 0T Codes That Nobody Notices

Here is the scenario that HMRC's own guidance does not highlight loudly enough. You start a new job, accept the first payslip, and assume the lower take-home is because of a pension contribution or some other deduction you have not yet figured out. Three months pass. Six months pass. Your 0T code is still active and the overpayment is now substantial.

This is not unusual. Research by consumer groups has consistently found that millions of UK workers do not check their tax code on their payslip, and many could not identify an incorrect one if they did. The code sits in small print next to your gross pay figure and most people simply look at the net amount.

If you have recently changed jobs or taken on a second income and have not actively confirmed your tax code, right now is the moment to check your tax code at /check-my-tax-code. It takes under five minutes and could confirm you are owed several hundred pounds.

For a broader look at the signs that your PAYE deductions might be wrong, Am I Overpaying Tax? Six Silent Signs Your Code Is Wrong covers the full range of scenarios beyond just 0T.

One Number That Should Not Be Ignored

A zero is usually a neutral figure. In tax code terms, it is anything but. The 0T emergency code is HMRC's way of saying it does not have enough information to treat you fairly, and the cost of that informational gap falls entirely on you until you correct it.

The fix is available, the overpaid tax is reclaimable, and the process, while imperfect, does work. But HMRC will not chase you to return your own money. That first step has to come from you.

Start by confirming exactly what code HMRC is currently operating for every source of your PAYE income. Check your tax code free at /check-my-tax-code and find out whether that zero is quietly draining your pay packet right now.

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