Tax codes one by one
T tax code
A letter that changes nothing in the arithmetic, but a lot in how HMRC handles your code.
Tax-free pay from this job
£12,570 a year
- 1257 × 10 = £12,570, and the letter T means your allowance includes other calculations by HMRC.
- England or Northern Ireland rates
- Cumulative: allowance and bands build up through the tax year, so over- or under-payments correct themselves
| Tax-free pay each month | £1,048.26 |
| Tax over the year on £30,000 | £3,484.00 |
| That is, each month | £290.33 |
| With 1257L instead | £3,484.00 |
Estimate with HMRC’s payroll method and the same pay every month. Only HMRC can change your code.
A tax code ending in T, such as 1257T or 1150T, means your Personal Allowance includes other calculations. GOV.UK gives exactly that definition, and the employer guidance adds that T is used when HMRC has to go through some items with you. For your pay, the T works like an L. The number is still the tax-free amount with the last digit dropped, the free pay is the same, and the pay above it is taxed at 20, 40, 45% according to the bands for 2026 to 2027. On £30,000 a year, 1257T takes £3,484.00, the same as 1257L. The difference is administrative. HMRC's PAYE specification says the suffix plays no part in the tax calculation; it tells employers which codes they may change themselves when HMRC issues a general uplift. Codes ending in L, M or N can be raised that way, but T codes cannot: HMRC amends them one by one with an individual notice. If your code ends in T, check the items behind it in your HMRC online account.
What a new code number changes
Change in tax each month
+£17.83
| Allowance change | −£1,070 |
| Tax over the year with 1257L | £3,484.00 |
| Tax over the year with 1150L | £3,698.00 |
Rules read on HMRC’s texts by Radif Partners · Editorial policy · Method
What the T changes, and what it does not
Every suffix letter sits at the end of a number. The number is what the payroll uses: multiply it by ten for the yearly tax-free amount, then spread it across the weeks or months using HMRC's tables. The letter only labels the situation. For L, that label is the standard allowance; for M and N, a Marriage Allowance transfer; for T, an allowance worked out with other calculations that HMRC wants to keep under review.
| Code | Tax-free a year | Free pay each month | Yearly pay | Tax with the T code | Tax with the same number and L |
|---|---|---|---|---|---|
| 1257T | £12,570 | £1,048.26 | £30,000 | £3,484.00 | £3,484.00 |
| 1150T | £11,500 | £959.09 | £30,000 | £3,698.00 | £3,698.00 |
| 1050T | £10,500 | £875.76 | £42,000 | £6,298.00 | £6,298.00 |
| 900T | £9,000 | £750.76 | £25,000 | £3,198.00 | £3,198.00 |
The last two columns are equal on every line. If your code moved from 1257L to 1150T, the extra tax comes from the lower number, not from the T.
Why HMRC keeps T codes apart
The PAYE specification explains what suffixes are really for. When HMRC raises allowances, it can send a general authority to every employer: form P7X for a change during the year, form P9X for a change from 6 April. Employers then add the same amount to every code carrying the suffixes named in it, which are L, M and N. Prefix codes such as BR, D0 or K are not changed that way, and neither are codes ending in T. Those are amended, where needed, by an individual notice from HMRC, a form P6 during the year or a P9 for the new year.
In practice, a T code is one that HMRC reviews individually rather than letting it move with a general change. For the coming year, HMRC's P9X notice tells employers to carry forward the existing code for anyone who does not receive a new one, so a T code simply continues on 6 April unless HMRC sends a replacement.
Tax-free pay behind a code number
Tax-free a year
£11,500
| Free pay in month 1 | £959.09 |
| Free pay in week 1 | £221.34 |
| Against the Personal Allowance | −£1,070 |
HMRC’s tables add £9 to the code number × 10, so the free pay is a few pence above a twelfth of it.
What to do when your code ends in T
A T code is not a mistake in itself. It is worth checking, though, because the review it signals can lag behind your real situation. Sign in to your HMRC online account and look at the calculation of your allowance: the starting Personal Allowance of £12,570, every deduction taken off and every addition made, and the income HMRC expects you to receive this year. Compare it with your payslips and with any benefits or expenses you know about.
If something is wrong, update it there. GOV.UK's page on updating a tax code says HMRC then sends the new code to you and your employer within 15 working days, and it should reach a monthly payslip within one or two pay days. Once the items under review are settled, the code may return to an L with the right number, or keep the T with an updated one.
T codes next to the other letters
Do not confuse the suffix with the T inside 0T and NT. The specification treats T as the suffix of both: 0T is a zero allowance with the normal bands, and NT means no tax at all. A code such as 1257T has a real allowance and normal rates. The table of letters places T among all the others, and the page on code numbers shows how the number in front is built.