Income Tax UK: How It Actually Works (2026/27)

The first year I earned over £100,000, I assumed I knew how tax worked. I’d been running a business, reading spreadsheets, managing payroll. Then I saw my self-assessment bill and genuinely thought there was a mistake. There wasn’t. I just didn’t understand how income tax actually worked at the higher end. And I suspect most people earning good money in the UK are in the same boat.

So let me break it down properly. Not the textbook version. The version I wish someone had explained to me ten years ago.

It’s not “you earn £50K so you pay 40% on everything”

This is the single biggest misconception about income tax, and I hear it constantly. People think that crossing into the higher rate band means all their income gets taxed at 40%. It doesn’t. The UK uses a progressive tax system, which means different portions of your income are taxed at different rates.

Think of it as filling up buckets. The first bucket is tax-free. The second bucket is taxed at 20%. The third at 40%. And so on. You only pay the higher rate on the money that falls into that specific bucket.

The personal allowance: your tax-free bucket

For the 2026/27 tax year, the personal allowance is £12,570. This is the amount you can earn before paying any income tax at all. It has been frozen at this level since 2021/22, and the government has confirmed it will stay frozen until at least April 2028.

That freeze matters. Wages have risen, inflation has pushed costs up, and the threshold hasn’t moved. More people are paying more tax in real terms than they were five years ago, even if their lifestyle hasn’t changed. This is called fiscal drag, and it’s one of the quietest tax increases the government has ever pulled off.

The tax bands: what you actually pay

Here are the income tax rates for England, Wales, and Northern Ireland in 2026/27:

Band	Taxable income	Rate
Personal allowance	Up to £12,570	0%
Basic rate	£12,571 to £50,270	20%
Higher rate	£50,271 to £125,140	40%
Additional rate	Over £125,140	45%

Worked example

Let’s say you earn £55,000 a year.

The first £12,570 is tax-free: £0
The next £37,700 (from £12,571 to £50,270) is taxed at 20%: £7,540
The remaining £4,730 (from £50,271 to £55,000) is taxed at 40%: £1,892
Total income tax: £9,432

Your effective tax rate on £55,000 is about 17.1%. Not 40%. Not even close. The 40% only applies to the slice above £50,270.

Scotland plays by different rules

If you’re a Scottish taxpayer, you have your own set of rates and bands. Scotland has six income tax bands instead of four:

Band	Taxable income	Rate
Personal allowance	Up to £12,570	0%
Starter rate	£12,571 to £14,876	19%
Basic rate	£14,877 to £26,561	20%
Intermediate rate	£26,562 to £43,662	21%
Higher rate	£43,663 to £75,000	42%
Advanced rate	£75,001 to £125,140	45%
Top rate	Over £125,140	48%

The higher rate kicks in earlier in Scotland (£43,663 versus £50,271 in the rest of the UK), and the top rate is 48% rather than 45%. If you earn above £75,000 in Scotland, you’re paying more than your English counterpart. Worth knowing if you’re considering a role north of the border.

The £100K trap: where it gets ugly

This is the part that caught me off guard. When your income goes above £100,000, you start losing your personal allowance. For every £2 you earn above £100K, you lose £1 of your £12,570 allowance. By the time you reach £125,140, your personal allowance is gone entirely.

The result? Between £100,000 and £125,140, your effective marginal tax rate is 60%. You’re paying 40% income tax, but you’re also paying tax on income that was previously sheltered by the personal allowance. For every extra £1 you earn in that band, you keep just 40p.

I remember the first time I ran the numbers on this. I was earning around £110,000 from the business, feeling pleased with myself, and then realised I was handing over 60p of every pound between £100K and £110K. It felt wrong. It felt like a penalty for doing well. But it’s been the system for years, and most people don’t know about it until the bill arrives.

I’ve written a detailed breakdown of the £100K tax trap if you want the full picture and, more importantly, how to avoid it.

How to check your tax code

Your tax code tells HMRC how much tax-free income you’re entitled to. The standard code for 2026/27 is 1257L, which means you get the full £12,570 personal allowance.

If your code is different, it usually means HMRC is adjusting for something: untaxed income, benefits in kind, underpaid tax from a previous year, or the personal allowance taper.

You can check your tax code by:

Looking at your payslip (it’s usually near the top)
Logging into your Personal Tax Account on gov.uk
Checking your P2 coding notice (HMRC sends this at the start of each tax year)

If your tax code looks wrong, don’t ignore it. Call HMRC or update your details online. An incorrect code can mean you overpay or underpay tax for months, and sorting it out retrospectively is a headache.

Tax-free allowances most people miss

Beyond the personal allowance, there are a few other allowances that can reduce your tax bill:

Marriage allowance. If one of you earns under £12,570 and the other is a basic rate taxpayer, you can transfer £1,260 of unused personal allowance to your spouse. That’s worth £252 a year, and you can backdate it four years. Free money that millions of couples don’t claim.

Blind person’s allowance. If you’re registered as blind (or severely sight impaired), you get an additional £3,070 on top of your personal allowance. This one is rarely discussed but it’s a meaningful reduction for those who qualify.

Trading allowance. If you earn up to £1,000 from self-employment or casual work, it’s completely tax-free. You don’t even need to report it. Handy if you do the odd bit of freelance work on the side.

Dividend allowance. The first £500 of dividend income is tax-free (down from £1,000 in 2023/24 and £2,000 in 2022/23). If you’re a company director paying yourself in dividends, this one has been slowly chipped away.

Savings allowance. Basic rate taxpayers can earn up to £1,000 in savings interest tax-free. Higher rate taxpayers get £500. Additional rate taxpayers get nothing. If you have significant savings outside an ISA, this is worth tracking.

The thing nobody tells you

The UK tax system isn’t designed to be simple. It’s designed to collect revenue, and complexity is a feature, not a bug. The people who pay the least tax relative to their income are the ones who understand the rules, or pay an accountant who does.

When I was building my business to £2.2M revenue, the single best investment I made was a good accountant. Not the cheapest one. The one who understood the system well enough to keep me on the right side of the law while making sure I wasn’t paying a penny more than I owed.

You don’t need to become a tax expert. But you do need to understand the basics: how the bands work, what your tax code means, and where the traps are. That knowledge alone is probably worth a few hundred pounds a year to you.

If you’re earning above £50,000, it’s worth a lot more than that.