Understanding Your P45 When Changing Jobs

When you leave a job and start a new one, your employer will give you a P45 — a document that records your pay, tax, and National Insurance for the portion of the tax year you worked there. Understanding your P45 when changing jobs is essential: it tells your new employer how much tax to take and ensures you're not overcharged during the transition. This guide explains what each section means, when you'll receive it, and what to do with it.

What Is a P45 and Why It Matters

A P45 is a tax form issued by your old employer when you leave. Its full name is "Statement of Earnings and Tax Deducted." It records:

Your gross pay for the tax year to date
How much income tax your old employer has already deducted
Your National Insurance contributions paid so far
Your tax code at the point you left

Your new employer uses this information to set your tax code and work out how much tax to deduct from your first pay packet. Without it, your new employer has to guess — which often means deducting too much tax, leaving you chasing a refund later.

The P45 exists because the UK tax year runs from 6 April to 5 April, not from January to December. If you change jobs mid-year, your tax and NI have to be tracked across two employers. The P45 is the handoff document.

The Five Parts of Your P45

A P45 has five parts, though you'll usually only see Parts 1A and 1B (your copy). Here's what each section tells you:

Part 1A and 1B (Your copy) These are identical duplicates given to you. Keep at least one safe — you'll need it when you apply for a new job, a mortgage, or student finance (lenders want proof of recent income). Part 1A goes to HMRC; Part 1B is yours.

Part 2 (New employer's copy) Your new employer keeps this. It contains your tax code, gross pay to date, tax paid, and National Insurance category letter (usually A, C, or H). This is how they know what rate of tax to apply from day one.

Part 3 (Pension information) If you were in a workplace pension, this part confirms how much you and your employer contributed, and whether the scheme is contracted out of the State Pension (rare now — most schemes contracted back in by 2016). Your new pension scheme needs to know this to avoid duplicate contributions.

Parts 4 and 5 These are rarely used now — they were for special circumstances like multiple jobs or pension transfers.

The key numbers on your P45 are:

Box 1a: Gross pay — everything you earned before tax, NI, or pension
Box 1b: Taxable pay — gross pay minus any pension contributions or other tax-deductible deductions
Box 2: Tax paid — the income tax already deducted this tax year
Box 5: National Insurance contributions — what you've paid so far
Box 6: Tax code — the code your new employer should use (more on this below)

When Do You Get Your P45?

Your old employer must give you a P45 by the 14th day after you leave — that's roughly two weeks. If you're leaving immediately, you should get it before your final payslip. If you're working notice, you may get it after your notice period ends.

If you're paid weekly: You might get your P45 within days. If you're paid monthly: If you leave mid-month, it may take longer since they need to process your final pay.

You can chase your old employer if you don't receive it within two weeks. HMRC can step in if there's a dispute, but it's faster to ask your payroll team directly.

What to Do With Your P45 at Your New Job

As soon as you start your new job, give your P45 to your new employer's payroll team — don't wait for them to ask. Ideally, do this on day one or before.

Your new employer will:

Use the tax code on Part 2 to set your initial tax deduction rate
Add your pay from your old job to their records
Make sure you're not taxed twice on the same income

If you give your P45 to your new employer before your first payday, you should be taxed correctly from the start. Your first payslip might look slightly different because it's a partial month, but the tax should be right.

Important: Don't lose your copy (Part 1A or 1B). You'll need it for:

Mortgage applications (lenders want recent payslips and P45s as proof of income)
Self-assessment tax returns (if you're self-employed later)
Disputes with HMRC about your tax code
Proving employment history

Store it with your other financial documents for at least 6 years.

What Happens If You Don't Have a P45?

If your old employer hasn't given you one yet (it happens — payroll departments are human), tell your new employer. They'll give you an emergency tax code until the P45 arrives. The most common emergency code is 1257L, which assumes you're using your full personal allowance.

Emergency tax codes often deduct more tax than you should pay — hence "emergency." You're not being punished; it's just the safe default. Once HMRC receives your P45 from your old employer, your tax code will be corrected, and you'll get a refund if you've overpaid.

If your old employer has gone bust or dissolved, HMRC knows (they receive P45s electronically). This is rare but happens in insolvency. You'll still get an emergency code at your new job, and HMRC will sort it once they receive any paperwork from the insolvency process.

If you're changing jobs multiple times in one tax year, each previous employer sends a P45. Your new employer needs to see them all to calculate tax correctly. If you're juggling three jobs simultaneously, bring all three P45s to each employer so they can coordinate.

Tax Codes Explained

The tax code on your P45 (usually something like 1257L) tells your employer how much of your income is tax-free. The number 1257 means you get a personal allowance of £12,570 (which is correct for 2026 — the code updates each April). The letter L means you're on a standard allowance code.

When you change jobs, your tax code carries forward — so if you were on code 1257L at your old job, you'll usually be on 1257L at your new one. Your new employer reads this from your P45 Part 2.

Common variations:

1257L: Standard personal allowance (most people)
0T: No personal allowance (you've earned more than £125,140 or have a second job)
D0 or D1: Emergency codes for higher earners
BR: Basic rate on all income (older second-job code)
K: You owe tax from a previous year

HMRC can change your tax code in April each year if your circumstances change (salary rise, new pension). Your old employer would have told you if they knew a change was coming. But the code on your P45 is what you actually used up to the day you left — that's what matters for the handoff.

Salary Changes and How They Affect Tax

When you negotiate salary for a new job, remember that the tax calculation depends on your total income for the tax year — not just your new salary.

Example: You earned £35,000 at your old job and left in December. You then start a new job at £42,000 in January. For the remainder of the tax year (5 months), you'll earn about £17,500 from the new job. Your P45 shows your old employer has already deducted tax on the £35,000. Your new employer will use your tax code to deduct the right amount from the £17,500, so you don't pay double tax.

If you're earning more at your new job, your new employer might switch you to an emergency code (usually BR — basic rate on all income) until HMRC confirms your tax code. This deducts 20% on everything, which often feels like too much. It's not — it's just a safe default. Once HMRC processes your P45, they'll send your new employer an updated code, and you'll get a refund.

Our UK salary calculator lets you model your take-home pay at your new salary, but remember that the tax depends on your total income for the year and whether you meet any thresholds (like the £100,000 personal allowance cliff).

Frequently Asked Questions

Q: Do I have to give my P45 to my new employer? A: Not legally — you can't be forced to. But you should. If you don't, your new employer will use an emergency tax code, which usually means overpaying tax. It's in your interest to hand it over.

Q: What if I start a new job before receiving my P45? A: Tell your new employer on day one. They'll use an emergency code temporarily. Once the P45 arrives (usually within two weeks), payroll will correct your tax code and any overpayment will be refunded.

Q: Can my old employer refuse to give me a P45? A: No. They're legally required to issue one by the 14th day after you leave. If they refuse or delay, contact HMRC — they can enforce it. It's rare but worth knowing.

Q: Do I need my P45 for a new job application? A: Most employers won't ask for it until you've accepted. They might want a recent payslip as proof of current employment, but the P45 comes later. Have it ready for your first day.

Q: If I'm starting as self-employed, do I need my P45? A: You'll need it for your tax return to HMRC — it shows your employment income for the tax year. Hang on to it.

Q: What if I've lost my P45? A: You can ask your old employer for a duplicate, or contact HMRC. It's easier to ask the employer — they'll usually email a copy. HMRC can retrieve it from their records, but it takes longer.

Q: Will my new employer see my old salary? A: Only the tax information on the P45 (gross pay to date, tax paid). They won't see your payslips or personal details from your old job — just the tax handoff. Your salary negotiations with them are separate.

Q: What if I'm changing jobs and also getting a pension transfer? A: Give both your old and new employer copies of the P45. The pension part (Part 3) confirms you're leaving that scheme. You and your new employer can then set up your new pension without duplicate contributions. Read more about pension transfers here.

Q: Can I claim tax relief on the journey to my new job? A: Only if you're self-employed or travel between multiple workplaces in a single day. If you have a single workplace, it's considered "normal commuting" and isn't tax-deductible. See our post on the real cost of commuting for more detail.

Your P45 is simple once you know what it is: a tax handoff between two employers. Get it, hand it to your new payroll team on day one, and keep a copy for your records. That's the whole process.