Tax Code 1100T Explained

What does 1100T mean?

1100T combines a reduced allowance of £11,000 with the T marker. Like 1257T, the T tells payroll software not to apply automatic uplifts at the start of the next tax year — HMRC will issue a corrected P2 once whatever review is outstanding (residency, multiple sources, P11D figures) has concluded. The reduced allowance reflects a £1,570 deduction from the standard amount, typically a benefit-in-kind or prior-year underpayment. Always cross-reference the components on your latest P2.

Breakdown of the code

• 1100

  Number

  £11,000 of personal allowance.

• T

  Letter

  Items in your tax affairs are under HMRC review — code will not auto-uplift.

Worked example

Director with multiple income streams under review on £60,000 (paid monthly).

~£817/month tax — code will need manual reissue at year end.

Who should be on 1100T?

• Taxpayers under HMRC review with a non-standard allowance figure

Common problems

• T persists into the next year because the review is not complete.
• Underlying review reasons are not documented on the P2.

What to do if 1100T looks wrong

1. Sign in to your HMRC personal tax account at gov.uk/personal-tax-account and open the latest P2 (Notice of Coding) — it itemises every adjustment.
2. Compare the code on your most recent payslip with the code HMRC has on file; employers occasionally apply an old code if a P9 was missed.
3. Confirm your employer received your P45, or that you completed a starter checklist if you joined mid-year.
4. Check whether benefits-in-kind such as a company car, fuel, or medical insurance have changed and ask payroll to file an updated P11D.
5. Call HMRC on 0300 200 3300 (Mon–Fri, 8am–6pm) with your National Insurance number if the online tools cannot resolve it.
6. If you have overpaid, HMRC normally refunds via your next payslip once the code is corrected. For closed years request a P800 review.

If you should be on a different code…

Quick decision tree — when 1100T is the wrong fit, here is the most likely correct code.

• If you have a single PAYE job and no benefits-in-kind — you should be on 1257L.

  Standard personal allowance of £12,570 for England, Wales and NI.