A T1 tax code means HMRC has set your tax-free personal allowance for the year at just £10. The number in any PAYE code multiplied by ten gives your annual tax-free income, so a “1” leaves you with virtually no shelter from tax, and the “T” tells your employer that HMRC calculated that figure deliberately rather than applying the standard allowance. For most people who see T1 on a payslip, it is either the result of the high-income taper that removes the personal allowance above £100,000 or a holding code while HMRC works out your position.
What the Code Is Telling Your Employer
Every PAYE code is a number followed by one or more letters. The number, times ten, is your tax-free allowance for the year. The letter tells payroll which rules to apply. The most common code for 2026-27 is 1257L, giving the full £12,570 personal allowance with no special adjustments.1GOV.UK. Income Tax Personal Allowance and the Basic Rate Limit From 6 April 2026 to 5 April 20282GOV.UK. Tax Codes – What Your Tax Code Means
With T1, the number gives you £10 tax-free for the whole year. The T suffix does two jobs. It signals that HMRC ran specific calculations to arrive at your allowance, and it blocks the automatic across-the-board adjustments payroll would otherwise apply when allowances change.2GOV.UK. Tax Codes – What Your Tax Code Means Any change to a T code has to come from HMRC as a fresh coding notice. Your employer cannot override it.3GOV.UK. Understanding Your Employees’ Tax Codes – What the Letters Mean
T1 is not the same as 0T, which you might also see near the bottom of the allowance scale. A 0T code gives you no tax-free income at all and is often applied when HMRC lacks the information for a proper code. T1 gives you £10 and signals a deliberate calculation.2GOV.UK. Tax Codes – What Your Tax Code Means
Why HMRC Would Assign T1
The single biggest reason is the personal allowance taper. Once your adjusted net income passes £100,000, the £12,570 allowance drops by £1 for every £2 you earn above the threshold, and disappears entirely at £125,140.4GOV.UK. Income Tax Rates and Personal Allowances Someone earning £125,120 has £10 of allowance left, which is exactly what T1 represents. Earnings around that point produce codes with very small numbers, and T1 sits at the end of that range.
The taper matters more each year because the £12,570 allowance has been frozen since April 2021 while wages have risen. People who were comfortably below £100,000 a few years ago find themselves crossing into the taper zone after routine pay rises, and their code changes to a T without any change in the rules themselves.
Beyond the taper, HMRC may use a T code when your affairs need manual oversight:
- Multiple income streams, such as rental income, dividends, or a second pension alongside employment, where a standard L code cannot carry the full picture.
- High-value taxable benefits like private medical insurance or a company car that reduce your available allowance.
- Unpaid tax from a previous year being collected through your code, which can pull the allowance low enough to trigger the T suffix.
- Incomplete information while HMRC waits on details of a new job, pension, or other income.
What T1 Does to Your Take-Home Pay
The impact is severe. Under 1257L, roughly £1,048 of each monthly payment is sheltered from tax. Under T1, only £10 of your entire year’s income is tax-free, so almost every pound is taxed from the first pay period at the appropriate rate.
Whether that is correct depends entirely on your income. Someone earning £130,000 has genuinely lost their allowance to the taper, and T1 or something close to it reflects reality. Someone earning £30,000 who has been placed on T1 by mistake pays roughly £2,500 more tax over the year than they should, which is about £200 a month gone from their payslip for no good reason. That gap is why checking the code matters, especially if your income has not crossed £100,000.
How to Check Whether T1 Is Right for You
Your code appears on your payslip, usually near your tax reference number. You can also see all your active codes across jobs and pensions through your personal tax account on GOV.UK.5GOV.UK. Personal Tax Account – Sign In or Set Up
Ask yourself a few questions. Is your total income from all sources above £100,000? If so, T1 or a similarly low T code is likely correct. Do you have significant taxable benefits, a second job, or a pension that HMRC might be factoring in? Do you owe tax from a previous year that HMRC is collecting through your code? If none of these applies and your income is well below the taper, the code probably needs correcting.
Before contacting HMRC, gather:
- Your P60, the end-of-year summary of pay and tax from each employer.6GOV.UK. Your P45, P60 and P11D Form – Why You Get Each Form
- Any P45 from a job you have left, showing pay and tax to your leaving date.
- Your P11D, which lists taxable benefits like company cars or medical insurance.7GOV.UK. Your P45, P60 and P11D Form – P11D
- Your best estimate of total earnings from all sources, including rent, dividends, and savings interest.
How to Get the Code Changed
The fastest route is the Check Your Income Tax service on GOV.UK. It lets you update your estimated income, report changes to company benefits, and tell HMRC about new income sources.8GOV.UK. Check Your Income Tax for the Current Year Once HMRC reviews the updated information, it issues a revised coding notice to your employer, and the new code takes effect from the next available pay period.
If you cannot use the online service, call the HMRC Income Tax helpline on 0300 200 3300, Monday to Friday, 8am to 6pm.9GOV.UK. Income Tax – Enquiries Have your National Insurance number and the documents above ready. Early mornings and midweek calls tend to move faster.
Contacting your employer will not fix anything. Payroll cannot change a T code without a notice from HMRC.3GOV.UK. Understanding Your Employees’ Tax Codes – What the Letters Mean
Getting Back What You Overpaid, or Settling What You Owe
After the tax year ends, HMRC reconciles what you earned against what was deducted. If the two do not match, you receive a P800 calculation letter, usually between June and October.
If you overpaid because T1 was wrong for your circumstances, you can claim the refund online through the link in your P800. Online refunds arrive in your bank account within five working days. If you prefer a cheque or do not claim online, HMRC posts one within 14 days of the letter’s date. A cheque requested by separate contact takes around six weeks.10GOV.UK. If Your Tax Calculation Letter (P800) Says You’re Due a Refund
If your circumstances mean you actually owed more than T1 collected, HMRC can recover under £3,000 by adjusting next year’s tax code, spreading the shortfall across 12 monthly deductions, provided any required returns were filed on time.11GOV.UK. Pay Your Self Assessment Tax Bill – Through Your Tax Code HMRC will not use this route if doing so would take more than 50 per cent of your PAYE income in tax or more than double your normal bill.
For amounts of £3,000 or more, HMRC may send a Simple Assessment letter, which asks for direct payment by the deadline stated on it.12GOV.UK. Pay Your Simple Assessment Tax Bill – Overview Interest on late payment stands at 7.75 per cent as of January 2026, high enough that prompt action pays off, especially where the original coding error was not your doing.13GOV.UK. HMRC Interest Rates for Late and Early Payments