I want to tell you something that took me an embarrassing amount of time to figure out.
When I got my first UK salary, I was expecting £1,500.
What landed in my account told a very different story.
They had deducted £850 in tax.
Now, I was new. I was fresh. I was also experiencing 24/7 electricity for the first time in my life, coming from Nigeria, uninterrupted power was already a miracle. So honestly? I was ready to let it go. I thought maybe this is just the price you pay for lights that actually stay on.
But something told me to make that call.
So I called HMRC.
They refunded me nearly £600.
Six hundred pounds. Sitting there. Mine. That I almost walked away from because I assumed the system had it right.
The problem was my tax code. I had OT on my payslip, which meant I was being taxed on every single pound I earned with zero personal allowance applied. It is one of the most common mistakes and most people never catch it.
So let me break this down properly. Because if nobody has ever sat you down and explained how UK tax actually works, this is that conversation.
Start Here: Your Tax Code
Before anything else, find your payslip and look for your tax code.
If you have one job, your tax code should be 1257L.
That is it. 1257L.
The number 1257 represents £12,570, the amount you can earn in a full tax year completely tax free. HMRC does not touch that money. It is yours. That is called your Personal Allowance.
The L at the end confirms that your standard Personal Allowance has been applied.
If your tax code says anything other than 1257L, if you see OT, BR, D0, or D1, something is wrong. You could be overpaying tax every single month without knowing it. Call HMRC on 0300 200 3300 and query it immediately. That one call could be worth hundreds of pounds.
How The Tax Bands Actually Work
Once you earn above £12,570, tax kicks in. But here is the thing most people get wrong , you do not pay the same rate on everything you earn. The system works in bands. You only pay the higher rate on the portion of income that falls within that band.
Here is how it breaks down for England, Wales and Northern Ireland:
£0 to £12,570 — Tax Free This is your Personal Allowance. You pay nothing on this.
£12,571 to £50,270 — Basic Rate (20%) You pay 20% on everything in this band. This is where most people in the UK sit.
£50,271 to £100,000 — Higher Rate (40%) You pay 40% on everything above £50,270. Once you hit this band, how you manage your tax becomes very important, and I will cover that in a separate post.
£100,001 to £125,140 — The Trap Most People Do Not Know Exists
This is where it gets really interesting.
Once you earn above £100,000, HMRC starts removing your Personal Allowance. For every £2 you earn above £100,000, you lose £1 of your Personal Allowance.
By the time you reach £125,140, your entire Personal Allowance is gone.
What that means in practice is that the effective tax rate in this band is not 40%.
It is 60%.
Sixty percent.
Most people earning in this range have absolutely no idea that band even exists. And if you are in it, or approaching it, you need to know this before your next paycheck.
Above £125,140 — Additional Rate (45%) You pay 45% with no Personal Allowance at all.
Now Let Us Talk About National Insurance
Income tax is not the only thing coming out of your payslip.
National Insurance is a separate deduction, and it is why your take home always feels lower than you expected.
Here is how it works for employees:
You pay 8% National Insurance on earnings between £12,570 and £50,270.
You pay 2% on everything above that.
So when people ask why their take home is so much lower than their salary, it is income tax and National Insurance combined. Two separate deductions. One payslip. One very confusing number at the bottom.
Let Me Make This Real With Actual Numbers
Say you earn £30,000 a year.
Your first £12,570 — completely tax free. The remaining £17,430 — taxed at 20%, which is £3,486 in income tax. Then National Insurance on top of that.
Your actual take home will be significantly lower than your gross salary. And if your tax code is wrong on top of all of that, it is even lower than it should be.
One More Thing; Scotland Is Different
If you are based in Scotland, your income tax bands are different. Scotland has six bands with rates running from 19% all the way up to 48%. Everything I have covered above applies to England, Wales and Northern Ireland only. If you are in Scotland, check the Scottish Government website for your specific rates.
What To Do Right Now
Find your payslip. Today.
Look for your tax code.
If you have one job and it is not 1257L, call HMRC on 0300 200 3300 and query it.
That one call could put hundreds of pounds back in your pocket.
And if you found this helpful, share it with someone who has never once looked at their payslip properly. You might just save them a small fortune.
