Tax Code Suffixes UK: What the Letter After the Number Does
Your tax code suffix silently controls how much PAYE you pay. This guide decodes every UK suffix letter and shows you when to challenge HMRC.
Your payslip has a tax code on it right now, and there is a reasonable chance the letter at the end of it is costing you money. Not because you did anything wrong, but because HMRC issues suffix letters automatically, based on assumptions that may no longer apply to your life.
This is a guide to every tax code suffix used in the UK PAYE system, what each one instructs your employer to do, and crucially, which ones are most likely to be wrong.
- The suffix letter in your tax code is not decorative. It tells your employer which tax-free allowance rules to apply to your pay.
- The letter L is by far the most common suffix, covering the standard Personal Allowance. If yours is anything else, there is a specific reason worth investigating.
- Suffixes like T and 0T can silently remove your Personal Allowance entirely, causing significant overpayments.
- HMRC assigns most suffix letters automatically using outdated or incomplete data. You have the right to challenge any code you believe is wrong.
- Checking your current tax code takes under two minutes at /check-my-tax-code, and the average overpayment reclaimed runs into hundreds of pounds.
What a Tax Code Suffix Actually Does
- Tax Code Suffix
- The letter or letters at the end of a UK PAYE tax code (for example, the 'L' in 1257L). The suffix instructs your employer's payroll software which set of tax-free allowance rules to apply when calculating how much income tax to deduct from your pay each period.
Most people know their tax code as a number followed by a letter, something like 1257L. The number represents your tax-free allowance divided by ten (so 1257 means £12,570 of untaxed income). But the letter is doing something equally important: it tells your employer's payroll system which rule set to follow.
Change the letter, and the amount of tax deducted from your next payslip changes, even if the number stays identical. That is why getting the suffix right matters as much as getting the number right.
HMRC currently operates a handful of suffix letters in active use, plus a few that appear only in specific circumstances. Here is each one, what it means, and what it might mean for you.
The L Suffix: The Baseline Everyone Should Understand
If your tax code ends in L, you are receiving the standard Personal Allowance for the current tax year, which is £12,570 in 2025-26. Your employer deducts tax only on earnings above that threshold.
L is the default. HMRC assigns it when no other circumstances apply. For the vast majority of employees on a single PAYE income below £100,000, with no untaxed income, no benefit in kind, and no Marriage Allowance adjustment, 1257L is exactly right.
But "the vast majority" is not everyone. If your code ends in L and you also receive a company car, private health insurance through work, or have a second job, the number may have been reduced to account for those benefits, but the L suffix itself would still be correct.
We have covered what the L suffix specifically means in detail elsewhere. The key point here: if you have L, your starting question is whether the number is accurate, not the letter.
The M and N Suffixes: Marriage Allowance in Action
These two are mirror images of each other, and both relate to the Marriage Allowance scheme. If you are married or in a civil partnership and one partner earns below the Personal Allowance threshold, the lower earner can transfer 10% of their allowance (£1,260 in 2025-26) to the higher earner.
M suffix: You are the recipient of a transferred Marriage Allowance. Your Personal Allowance is effectively boosted, so your code might read 1383M (1257 + 126 = 1383, displayed as the number multiplied by ten).
N suffix: You are the transferor. You have voluntarily surrendered part of your allowance to your partner. Your code will reflect the reduced allowance.
Where it goes wrong: HMRC continues applying M or N codes even after a marriage ends, a partner dies, or someone's income changes enough to make the transfer counterproductive. The Marriage Allowance transfer must be actively revoked if circumstances change. HMRC does not automatically remove it.
If you have an M or N suffix and your circumstances have changed, you may be under or overpaying. The M suffix and Marriage Allowance post covers the claiming side; the N suffix post explains what happens on the transferor side.
The T Suffix: HMRC Is Reviewing Your Code
A T suffix means HMRC needs to carry out further checks before finalising your tax code. In practice, it usually appears when:
- Your adjusted net income is between £100,000 and £125,140 (where the Personal Allowance is tapered away at £1 for every £2 earned above £100,000)
- There are multiple sources of income that HMRC cannot yet reconcile
- You have requested that your coding details are not shared with your employer in full
The T suffix does not, by itself, change how much tax you pay. It is more of a flag. But it is a flag that your tax situation is non-standard enough for HMRC's automated systems to pause.
If you have a T suffix and earn significantly above £100,000, you may be caught in the Personal Allowance taper. At £125,140, the allowance is withdrawn entirely, and a T code is one of the ways HMRC handles that calculation. At that income level, each £2 you earn above £100,000 costs you £1 of Personal Allowance, which translates to an effective marginal tax rate of 60% on income between those two figures.
That is not a typo. A 60% effective marginal rate is the mathematical consequence of the taper, and a T code is often your first visible signal that you are in that bracket.
The 0T Suffix: The One That Strips Everything
0T (zero T) is one of the most damaging codes an employee can receive, because it removes your Personal Allowance entirely. You pay income tax on every pound you earn from the first penny.
For a basic rate taxpayer earning £30,000, the difference between a correct L code and a 0T code is roughly £2,514 in additional tax per year. That is not a rounding error. That is a significant and recurring overcharge.
HMRC and employers issue 0T codes in several situations:
- You have started a new job and your employer has no P45 from your previous employment
- Your Personal Allowance has been used up against a different income source
- HMRC has not yet processed your tax code for the new tax year
- You are a higher earner whose allowance has been tapered to zero
The emergency use of 0T is technically legitimate as a temporary measure. The problem is that "temporary" sometimes lasts months, with no automatic correction.
If you are on a 0T code and it has been more than a few weeks since you started your new role, you are almost certainly overpaying. Check your current code now at /check-my-tax-code, and if you see 0T, act on it that same day.
The BR Suffix: Basic Rate on Everything
BR does not pair with a number in the usual way. It instructs your employer to deduct basic rate income tax (currently 20%) from every pound of that income, with no Personal Allowance applied at all.
BR codes are generally correct when applied to a second job or a second pension, where your Personal Allowance has already been allocated to your primary income source. If you earn £40,000 from your main job and £8,000 from a second role, the second employer should ideally be using BR.
Where it goes wrong: people with only one job, or people who have left a second job but whose former employer's BR code is still sitting on HMRC's system, occasionally find BR applied to their sole income. Every pound of that income is then taxed at 20% with no allowance. On an annual salary of £28,000, that is approximately £2,514 of Personal Allowance wasted.
If BR appears on your main job's payslip and it is your only employment, check and update your code immediately.
The D0 and D1 Suffixes: Higher and Additional Rate
These follow the same logic as BR but at higher rates.
D0: All income from this source taxed at the higher rate (40%), with no allowance.
D1: All income from this source taxed at the additional rate (45%), with no allowance.
D0 and D1 are normally applied to additional income streams where a high earner has already exhausted their basic rate band on their primary income. A director with a salary and a separate consultancy contract paid through PAYE, for example, might legitimately see D0 on the second income.
The risk: if HMRC's data suggests you are a high earner based on a previous year's income, and your earnings have since dropped, D0 or D1 can persist incorrectly. That means 40% or 45% deducted on income that should be taxed at 20%.
This is not an academic edge case. Employment changes, redundancies, and business downturns happen. HMRC's systems update annually in many cases, not in real time.
The K Suffix: When Tax Owed Exceeds Your Allowance
A K code is different from all the others because it works in the opposite direction. Instead of a tax-free allowance reducing your taxable income, a K code adds a notional amount to your income before tax is calculated.
This happens when the deductions HMRC needs to collect from you exceed your Personal Allowance. Common triggers include:
- A large company car or fuel benefit in kind
- State pension income being collected through a PAYE employment (where the pension itself is not taxed at source)
- Underpaid tax from a previous year being collected through PAYE
A K code might read K497, meaning £4,970 is added to your taxable income, rather than subtracted. On a salary of £30,000, you would be taxed as if you earned £34,970.
Important safeguard: HMRC caps the tax deducted under a K code at 50% of your gross pay for any pay period. Your employer cannot legally deduct more than half your wages due to a K code, however large the notional addition.
If you have a K code and are not sure why, the most likely culprit is a benefit in kind your employer reported to HMRC on a P11D. You can see what benefits are on record via your HMRC Personal Tax Account.
The NT Suffix: No Tax Deducted at All
NT stands for "no tax." Your employer deducts nothing. This is legitimate in a narrow set of circumstances, including:
- Payments to contractors who are not subject to PAYE (though most contractors fall under IR35 rules now)
- Certain pension drawdowns where tax is handled separately
- Non-UK residents whose income is not subject to UK taxation
For the average UK employee, an NT code should trigger immediate investigation. If your payslip shows NT and you are a UK-resident employee receiving a regular salary, something has gone wrong.
The Scottish Prefix: How S Changes Everything
If your code begins with S (such as S1257L), you are subject to Scottish income tax rates rather than the UK-wide rates. Scotland has its own set of bands and rates, set by the Scottish Parliament, which diverge from the rest of the UK at multiple points.
This matters because Scottish higher-rate taxpayers start paying more tax at a lower threshold than their English counterparts. The Scottish tax codes post covers the full rate comparison, but the key suffixes (L, M, N, T, K, 0T etc.) behave identically; it is simply the rate tables that differ.
If you live in Scotland but your employer is headquartered in England, errors in your prefix are more common than they should be. HMRC is responsible for issuing the correct code to your employer, but payroll teams occasionally override this.
How to Check Whether Your Suffix Is Correct Right Now
You do not need to understand every suffix in depth to protect yourself. You need to know three things:
- What is your current tax code (check your most recent payslip or P60)
- Does the suffix match your actual circumstances
- If not, how much might you be overpaying
The quickest way to answer questions one and two is to check your tax code at /check-my-tax-code. You can also log into your HMRC Personal Tax Account directly to see your current code and the breakdown behind it.
If you find a discrepancy, the step-by-step guide to changing your code online explains the process. If your employer has been made aware of an error and still has not corrected it, the tax code error post covers your escalation options.
And if you have been on the wrong code for more than one tax year, an overpayment reclaim may be possible going back four years. The amounts involved can be substantial: a person on a BR code instead of 1257L for two years on a £35,000 salary has overpaid approximately £5,028.
People also ask
The Suffix Your Payslip Has Right Now Is Worth Checking
We opened with the claim that the letter at the end of your tax code might be costing you money. Having run through every active suffix, it is clear that the risk is concentrated in a handful of codes: 0T, BR applied to a sole income, D0 or D1 on reduced earnings, and K codes based on benefits no longer received.
If any of those descriptions sound familiar, the cost of inaction is measurable in hundreds or thousands of pounds per year, not a bureaucratic abstraction.
The entire PAYE system is built on the assumption that HMRC holds accurate, current data about your employment and income. Research by the Low Incomes Tax Reform Group suggests that up to one in three employees will have an incorrect tax code at some point in their working life. The suffix is one half of that code, and it is the half most people have never thought to question.
Your payslip is sitting on your phone or in your email right now. Take thirty seconds to find the tax code, identify the suffix letter, and match it against this guide. If something does not fit, check your code for free at /check-my-tax-code. That is the concrete next step. Everything else can wait.
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