Tax code · 2026/27

C1100L means you can earn £11,000 a year before paying income tax

Tax code C1100L gives you a tax-free personal allowance of £11,000 for the 2026/27 tax year, which is £917 a month or £212 a week. Anything you earn above that is taxed at the Welsh rates, starting at 20%. The number is simply your allowance with the last digit removed.

What does each part of C1100L mean?

The number 1100 is your allowance divided by 10: 1100 × 10 = £11,000. HMRC actually lets you earn up to £11,009 before tax because the last digit is dropped.
This allowance is £1,570 lower than the standard £12,570. Common reasons are taxable benefits such as a company car or medical insurance, untaxed income like interest or rent, underpaid tax from an earlier year being collected, or the allowance being tapered because your income is above £100,000.
The L suffix means you are entitled to the standard tax-free personal allowance, with no marriage allowance adjustment.
The C prefix means you are a Welsh taxpayer. Welsh rates are currently the same as those in England and Northern Ireland.

How much tax do you pay with code C1100L?

The table shows income tax and take-home pay in 2026/27 for four salaries with code C1100L, compared with the standard code 1257L. National Insurance is not affected by your tax code.

Salary	Tax with C1100L	Tax on standard code	Take-home with C1100L	Per month
£25,000	£2,800	£2,486	£21,206	£1,767
£35,000	£4,800	£4,486	£28,406	£2,367
£50,000	£8,060	£7,486	£38,946	£3,245
£75,000	£18,060	£17,432	£53,429	£4,452

On £35,000 the effective rate with C1100L is 18.8%, against 17.9% on the standard code, a difference of £314 a year. Use the take-home pay calculator with your own salary, pension and student loan.

Frequently asked questions

Is tax code C1100L correct for me?

Compare C1100L with the standard code 1257L. The difference should match an adjustment you recognise, such as a company benefit, job expenses, Marriage Allowance or an underpayment from an earlier year. If it does not, ask HMRC to review it.

How much tax do I pay on £35,000 with tax code C1100L?

On £35,000 with code C1100L income tax is £4,800 a year in 2026/27, leaving take-home pay of £28,406 (£2,367 a month) after National Insurance of £1,794. On the standard code it would be £4,486.

How do I change tax code C1100L?

You cannot change it yourself; only HMRC can issue a new code. Update your details in your HMRC Personal Tax Account or call 0300 200 3300 with your National Insurance number and details of your income and benefits. HMRC sends the new code to your employer and any tax overpaid in the year is refunded through your pay.

What does the C prefix mean?

The C prefix means HMRC has recorded your main home as being in Wales. The Welsh Government sets Welsh rates, which are currently the same as England's, so the code makes no difference to your tax today.