Know your tax code (and if it’s right)

Most contractors pay close attention to their rate, deductions and take-home pay, but how often do you take a closer look at your tax code?

It might look like a random mix of numbers and letters on your payslip, but your tax code plays an important part in determining how much tax you pay. If it’s wrong, you could end up paying too much tax now, or facing an unexpected fine later.

The good news is that understanding the basics is easier than you might think.

What is a tax code? 

Your tax code tells your employer or payroll provider how much tax-free income you’re entitled to during the tax year and how much income tax should be deducted from your pay. 

HMRC uses information it holds about your earnings, benefits and personal circumstances to calculate it. 

You’ll find your tax code on your payslip, P60 or within your HMRC Personal Tax Account. .

What does 1257L mean?

For most people, the standard tax code is 1257L. In fact, if you have one job and no unusual tax circumstances, this is probably the code you’ll see on your payslip.

Here’s how it breaks down:

• 1257 represents the standard Personal Allowance of £12,570
• L means you’re entitled to the standard tax-free allowance

In simple terms, you can earn up to £12,570 before paying Income Tax, with anything above that taxed at the appropriate rate.

Common tax codes contractors may see

While 1257L is the most common code, it’s far from the only one.

BR

BR stands for Basic Rate. It means all income from that employment is taxed at 20%, with no Personal Allowance applied.

This often appears when you have a second job or HMRC hasn’t yet allocated your tax-free allowance correctly.

D0 and D1

These codes are typically used where HMRC believes all earnings from that employment should be taxed at higher rates.

• D0 : all income taxed at 40%
• D1 : all income taxed at 45%

These are often seen on secondary sources of income.

0T

A 0T tax code means no Personal Allowance is being applied at all. This can happen when HMRC doesn’t have enough information about your circumstances or while records are being updated.

K codes

A K code indicates that deductions or taxable benefits exceed your available Personal Allowance. This can happen if you owe tax from previous years or receive taxable benefits that need to be collected through PAYE.

Emergency tax codes (W1, M1 or X)

If you’ve recently started a new assignment, changed employers or HMRC doesn’t yet have complete information, you may be placed on an emergency tax code.

These often appear as:

• 1257L W1
• 1257L M1
• 1257L X

Under an emergency code, tax is calculated based only on that week’s or month’s pay, rather than your earnings across the tax year. This can sometimes result in paying more tax than necessary until your records are updated.

Why tax codes go wrong

Tax codes aren’t static. HMRC updates them as your circumstances change.

Here are some of the most common reasons a  tax code may be incorrect:

• Starting a new contract or changing employers
• Working multiple assignments at the same time
• Having a gap between contracts
• Receiving taxable benefits
• Moving from self-employment into PAYE work
• Previous underpayments or overpayments of tax
• Changes to pension income or savings income

In many cases, HMRC just doesn’t have the full picture immediately, especially when you’ve recently changed working arrangements.

What happens if your tax code is wrong?

If your tax code is incorrect, it can affect how much tax you pay. In some cases, you may pay too much tax, meaning money that should be in your pocket is instead sitting with HMRC until the issue is identified and corrected. 

In others, you may not pay enough tax, which could result in HMRC recovering the shortfall later through a tax code adjustment or a tax calculation. Either way, checking that your tax code is correct can help you avoid unnecessary surprises and ensure you’re paying the right amount of tax throughout the year. 

Why it’s worth checking

Recent reports suggest millions of UK taxpayers may be paying the wrong amount of tax because of incorrect or outdated tax codes. Changes in employment, benefits, savings income and other adjustments can all create discrepancies if HMRC’s records aren’t up to date.

That’s why it’s worth spending a few minutes checking your tax code whenever:

• You start a new assignment
• You receive a tax code notice from HMRC
• Your circumstances change
• Something on your payslip doesn’t look right

How to check if your tax code is right

Start by asking yourself a few simple questions:

• Do I have more than one source of income?
• Have I recently changed jobs or assignments?
• Do I receive any taxable benefits?
• Have I received any letters from HMRC about my tax code?

You can then check your tax code through:

• Your payslip
• Your HMRC Personal Tax Account
• The HMRC app
• Any coding notices you’ve received from HMRC

If the code doesn’t seem to match your circumstances, it’s worth investigating further rather than assuming it’s correct.

Need help understanding your payslip?

Tax codes can be confusing, especially when you’ve recently changed assignments, have multiple income sources or spot a code you’ve never seen before.

While only HMRC can confirm and amend your tax code, the Contractor Care Team at Liquid Friday is always happy to help you understand what you’re seeing on your payslip, explain what your tax code may mean, and point you towards the right HMRC resources or next steps.

If something doesn’t look right, don’t ignore it. A quick check today could save you money, stress and unexpected surprises further down the line.