Understanding Your Tax Code UK — What the Numbers Mean

Your tax code determines how much tax is taken from your pay. Here’s what it means and how to check it’s correct.

What Is a Tax Code?

The Purpose

What It Does	Details
Tells employer	How much tax to take
Reflects your allowances	Personal Allowance and adjustments
Applied to payroll	Automatically deducted
Different for each job	If you have multiple

Where You Find It

Location	Details
Payslip	Usually near tax information
P60	Annual summary
P45	When leaving a job
HMRC online	Personal Tax Account
Tax code notice	Letter from HMRC

How to Read a Tax Code

The Number Part

How It Works	Example
Multiply by 10	Your tax-free amount
1257 = £12,570	Standard Personal Allowance
1100 = £11,000	Reduced allowance
500 = £5,000	Much reduced allowance

Common Letters

Letter	Meaning
L	Standard Personal Allowance
M	Marriage Allowance received
N	Marriage Allowance transferred away
T	Allowance includes other calculations
0T	No Personal Allowance
BR	All income taxed at basic rate (20%)
D0	All income taxed at higher rate (40%)
D1	All income taxed at additional rate (45%)
NT	No tax (tax-free income)
S	Scottish taxpayer
C	Welsh taxpayer

Common Tax Codes Explained

1257L

Meaning	Details
What	Standard code for most people
Tax-free	£12,570 (1257 × 10)
Who gets it	One job, standard allowance
Should you have it	If straightforward situation

1257L M

Meaning	Details
What	Receiving Marriage Allowance
Tax-free	£13,830 (extra from spouse)
Who gets it	Spouse transferred allowance to you

BR

Meaning	Details
What	Basic Rate on everything
Tax-free	£0
Who gets it	Second job (allowance used on first)
All income	Taxed at 20%

D0

Meaning	Details
What	Higher Rate on everything
Tax-free	£0
Who gets it	Second job when earning enough
All income	Taxed at 40%

0T

Meaning	Details
What	No allowance given
Tax-free	£0
Why	HMRC doesn’t have info or allowance used
Result	Tax on everything

K Code

Meaning	Details
What	More to tax than allowance
Example	K500
Why	Benefits in kind exceed allowance
Result	Extra tax collected through PAYE

Examples

Code	Tax-Free Amount	Typical Reason
1257L	£12,570	Standard
1000L	£10,000	Benefits reducing allowance
BR	£0	Second job
S1257L	£12,570	Scottish taxpayer
K500	Negative (owe £5,000 extra)	High benefits in kind

How Your Code Is Calculated

Standard Calculation

Step	Example
Start with Personal Allowance	£12,570
Add any extra allowances	+£0
Subtract benefits in kind	-£2,000
Subtract underpaid tax	-£500
Result	£10,070
Code	1007L

What Reduces Your Code

Reduction	Why
Company car	Taxable benefit
Private medical insurance	Taxable benefit
Tax owed from previous year	Collected through code
State Pension	If also working
Other income	Being collected via code

What Increases Your Code

Addition	Why
Marriage Allowance	Receiving spouse’s transfer
Blind Person’s Allowance	Registered blind
Work expenses	HMRC agreed reliefs

Checking Your Tax Code

Is Your Code Right?

Check	What to Look For
Number close to 1257	If standard circumstances
Benefits in kind	Should reflect actual extras
Previous year balances	Should be repaid by now
Marriage Allowance	If claimed/receiving

Signs of a Wrong Code

Sign	Possible Problem
Much lower than 1257	Incorrect reduction applied
BR on only job	Allowance misallocated
0T on only job	HMRC missing information
K code unexpectedly	Benefits overstated

How to Check

Method	Details
HMRC online	Personal Tax Account shows breakdown
Tax code notice	Letter explaining calculation
Contact HMRC	If unclear

Fixing a Wrong Tax Code

Steps to Take

Step	Action
1	Log into Personal Tax Account
2	Check the calculation breakdown
3	Identify what’s wrong
4	Update information online or call HMRC
5	New code issued to employer

What HMRC Can Change

Issue	Solution
Wrong benefits listed	Remove/correct them
Allowance missing	Add it back
Wrong income estimated	Correct it
Previous year error	Adjust and refund/collect

Getting a Refund

Situation	What Happens
Overpaid this year	Adjusted in future pay
Overpaid previous years	Refund by cheque or into salary
Large overpayment	Apply for P800 refund

Multiple Jobs and Tax Codes

How It Works

Job	Typical Code
Main job	1257L (full allowance)
Second job	BR (no allowance)
Third job	BR (no allowance)

Splitting Your Allowance

Option	How
Split between jobs	Request from HMRC
All on one job	Standard approach
Why split	If income varies

Common Problems

Problem	Solution
Allowance on wrong job	Contact HMRC
No allowance at all	Check Personal Tax Account
Paying too much	HMRC will reconcile at year end

Emergency Tax Code

What Is It?

Feature	Details
When used	New job, no P45
Code	Often 1257L W1 or M1
Effect	Month-by-month (no cumulative)
Result	May overpay initially

How to Fix Emergency Tax

Step	Action
1	Give P45 to new employer
2	Or complete Starter Checklist
3	HMRC updates code
4	Excess tax refunded in subsequent pay

Summary: Tax Code Quick Reference

Common Codes

Code	Meaning
1257L	Standard — full allowance
BR	Basic rate on everything
D0	Higher rate on everything
0T	No allowance
K	You owe extra
S prefix	Scottish taxpayer
C prefix	Welsh taxpayer

Action Checklist

Action	When
Check code on payslip	Every new code
Review Personal Tax Account	At least annually
Query if number seems low	Below 1000 unexpectedly
Update HMRC	If circumstances change
Keep P45	For new employers

Your tax code directly affects your take-home pay. Understanding it helps you catch errors that could cost you money.