What does the tax code
1100L mean?
1100L was the standard UK code for 2016/17. Because the allowance changed most years back then, an old code is a reliable way of dating an undated payslip.
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Get the detailed breakdown + free reclaim guide1100L was the standard UK tax code for the 2016/17 tax year, giving £11,000 of tax-free pay. It has not been current for nine years.
Almost nobody arrives at this page because they are on the code. They arrive holding a payslip or a P60 with no obvious date on it, and the tax code is the most legible thing on the page. That turns out to be a genuinely useful thing to know how to do.
- 1100L Tax Code
- The standard UK tax code for the 2016/17 tax year, giving a Personal Allowance of £11,000. The L suffix meant the ordinary allowance rules applied with no adjustments. It was replaced by 1150L for 2017/18 when the allowance rose to £11,500.
Using a tax code to date a document
Between 2014 and 2021 the Personal Allowance rose almost every year, and the standard code moved with it. That makes the code a near-unique year marker for anything from that era.
| Standard code | Personal Allowance | Tax year |
|---|---|---|
| 1000L | £10,000 | 2014/15 |
| 1060L | £10,600 | 2015/16 |
| 1100L | £11,000 | 2016/17 |
| 1150L | £11,500 | 2017/18 |
| 1185L | £11,850 | 2018/19 |
| 1250L | £12,500 | 2019/20 and 2020/21 |
| 1257L | £12,570 | 2021/22 onwards |
Two cautions before relying on it.
1250L covers two years, so it narrows a document to 2019/20 or 2020/21 rather than pinning it exactly. 1257L covers six and counting, because the allowance has been frozen since 2021/22 and is set to stay frozen until at least April 2028. Anything from the last six years cannot be dated this way at all.
And of course the method only works on a standard code. If the person had a benefit in kind or an expenses claim, their code was never the standard figure for the year, and the table tells you nothing.
What it would cost today
1100L against today's standard allowance is a shortfall of £1,570.
On a £30,000 salary that means £19,000 of taxable income rather than £17,430, so £3,800 of tax against £3,486. The difference is £314 for the year, or about £26 a month. Income tax only, National Insurance excluded, and an estimate to confirm with HMRC.
That figure is worth carrying, because it is roughly what any long-stale code costs. The point is not that anyone is really on 1100L in 2026/27, but that a code left behind by a few years quietly costs a few hundred pounds a year without ever announcing itself.
The years you can and cannot reach
2016/17 is long closed. The general time limit for a tax claim is four years from the end of the tax year concerned, so that window shut on 5 April 2021.
As at August 2026 the open years are 2022/23, 2023/24, 2024/25 and 2025/26, plus the current 2026/27 which is still running. 2022/23 closes on 5 April 2027, and one further year drops out of reach every 6 April after that.
So the value in an old payslip is never the old year. It is the evidence. If your code was wrong in 2016/17 for a reason that never got fixed, the same reason was very likely still operating in 2022/23, and that year is claimable for a few more months. Our 1150L page works through the sliding window in detail, and our guide to reclaiming overpaid tax covers how a closed year is actually claimed.
What to keep, and for how long
Since old paperwork is what a claim is built from, it is worth knowing what matters.
P60s. One per employment per year, showing total pay and tax deducted. The single most useful document, and the hardest to replace.
Final payslips from jobs you left. These capture the year-to-date position at the point you left, which is exactly what goes missing when an employer record is closed badly.
P45s. Less critical once the year has been reconciled, but useful for reconstructing a messy year with several employments.
P2 coding notices. The only document that explains why a code was what it was. Most people throw these away, and they are the ones you want when arguing that a deduction was wrong.
P11Ds. Your employer's statement of the benefits they reported, which is what a coding deduction should reconcile to.
A reasonable rule is to keep everything covering the last four full tax years, because that is exactly the period you can still act on. Anything older is memorabilia rather than evidence.
When the code on a payslip is not the code HMRC issued
Dating a document from its code assumes the payslip shows the code that was actually in force. Often it does not, and knowing why saves a lot of confusion when two documents from the same year disagree.
Employers lag. A code issued by HMRC has to reach the payroll provider and be applied to the next available run. A code issued in late March can easily first appear on an April payslip, which puts it in the following tax year. So a payslip showing the previous year's code near the start of a year is normal rather than wrong.
Codes change mid-year. Nothing requires a code to last twelve months. Someone can be on three codes in one year if their circumstances move, and each payslip shows whichever was current at the time. A P60 shows the code in force at the end of the year, which may be none of the ones on the payslips you kept.
Emergency markers get dropped in printing. Older payslip layouts often had a narrow field for the code and truncated anything after it, so a code shown as "1100L" might really have been "1100L W1". That matters, because a non-cumulative code taxes each period in isolation and is the single most common cause of a genuine overpayment. Our 1257L M1 page works through what that costs.
Two employments show two codes. Each payslip only shows the code for that employment, so neither tells you the whole story on its own.
The rule that follows from all of this: date a document from the P60 wherever you have one, and use the code as a cross-check rather than the primary evidence.
One more thing the code cannot tell you: whether it was right. The table above gives the standard code for each year, but plenty of people were legitimately on something else, and plenty of others were on the wrong code entirely without knowing. A payslip showing 1100L in 2016/17 only tells you the code matched the standard for that year. It says nothing about whether the standard code was the correct one for that person's circumstances, which is a separate question and the one that actually carries money.
If a code really is stuck in the past
Occasionally a code genuinely has not been rebuilt for years, usually where an employment record was never closed properly or HMRC holds an address it cannot reach.
Check your current code first, on your latest payslip or in your Personal Tax Account at gov.uk/personal-tax-account. Our guide to checking your tax code covers where it appears on each document, and the wrong tax code page covers what to do when HMRC's record disagrees with yours.
Our free tax code checker will estimate what your code should be for each of the open years, which is a faster way of spotting a long-running error than reading years of notices. It gives an estimate rather than advice.
People also ask
- 1100L gave £11,000 of tax-free pay and was the standard code for 2016/17 only
- Standard codes changed almost every year until 2021, which makes them a reliable way to date old paperwork
- The method stops working from 2021/22, because 1257L has been standard for six years and counting
- 1100L against today's allowance would cost about £314 a year on a £30,000 salary
- 2016/17 closed to claims on 5 April 2021 and cannot be reopened
- The open years are 2022/23 through 2025/26, with 2022/23 closing on 5 April 2027
- Keep P60s, final payslips, coding notices and P11Ds for at least four full tax years
Related tax codes: 1150L tax code | 1250L tax code | 1000L tax code | 1257L tax code | Wrong tax code?
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