A 978L tax code means HMRC has given you a tax-free personal allowance of £9,780 for the year, which is £2,790 less than the standard £12,570. Your employer uses the code to work out how much income tax to take from each pay packet. The reduction almost always comes from a taxable benefit provided by your employer, tax owed from an earlier year, or untaxed state pension income that HMRC is collecting through your wages.
What the 978L Code Actually Says
Every PAYE code has a number and a letter. The number is your annual tax-free allowance with the last digit dropped: 978 becomes £9,780. Anything you earn above that in the tax year is taxable.
The L confirms you qualify for the standard personal allowance.1GOV.UK. Tax Codes: What Your Tax Code Means It’s the most common suffix in the system. What it doesn’t tell you is why your particular figure sits below the £12,570 baseline that most people on an L code receive. That answer lives in the deductions HMRC has applied behind the scenes.
The code stays in place for the rest of the tax year unless you or HMRC change it.
Why Your Allowance Was Reduced by £2,790
The standard allowance for 2025/26 and 2026/27 is £12,570.2GOV.UK. Income Tax Rates and Personal Allowances On a 978L code, £2,790 has been taken off. Several things can cause that reduction, and more than one can apply at once.
Benefits in Kind
The most common cause is a taxable perk from your employer. Private medical insurance, a company car, or an employer-paid gym membership all carry a taxable value. Your employer reports these on a P11D form each year, and HMRC subtracts that value from your allowance so the right amount of tax gets collected through your regular pay rather than in a later bill.3GOV.UK. Expenses and Benefits for Employers: Reporting and Paying
A £2,790 reduction is on the smaller side. It might reflect modest private medical cover, a combination of small perks, or a low-value company benefit rather than a full company car, which typically produces a much larger adjustment.
Tax Owed from a Previous Year
If you underpaid tax last year, HMRC often collects the shortfall by lowering this year’s allowance, spreading the repayment across twelve months of payslips. HMRC can only do this when the underpayment is less than £3,000.4GOV.UK. Pay Your Self Assessment Tax Bill: Through Your Tax Code For £3,000 or more, HMRC sends a Simple Assessment letter demanding direct payment instead.5GOV.UK. Pay Your Simple Assessment Tax Bill: Overview
State Pension Income
The state pension is taxable but paid without tax deducted. If you receive both a state pension and other income such as a workplace pension or wages, HMRC lowers the code on the other income to cover the tax due on the pension.6GOV.UK. Tax When You Get a Pension: How Your Tax Is Paid The full new state pension is £241.30 a week, roughly £12,548 a year.7GOV.UK. The New State Pension: What You’ll Get Even a partial state pension can eat noticeably into your allowance.
Reliefs You Might Be Missing
Reliefs push in the opposite direction. Fees paid to a professional body on HMRC’s approved list add to your allowance when claimed. If you’re entitled but haven’t claimed, your code may be lower than it needs to be.8GOV.UK. List of Approved Professional Organisations and Learned Societies (List 3) Worth checking, because many people miss it.
What 978L Costs You in Tax
The arithmetic is straightforward. Subtract £9,780 from your annual gross salary, then apply the standard rates. Take someone earning £40,000:
- Taxable income: £40,000 − £9,780 = £30,220
- Basic rate tax at 20%: £6,044 a year
- That’s around £503 a month in income tax
The same salary on the standard 1257L code would produce £5,486 in income tax. So 978L costs an extra £558 a year, or about £46.50 a month. That gap is how HMRC recovers tax on the £2,790 adjustment.
If your income crosses £50,270, the 40% higher rate kicks in on earnings above that point, up to £125,140.2GOV.UK. Income Tax Rates and Personal Allowances
Two things your tax code doesn’t touch: National Insurance and student loans. NI for 2026/27 is 8% on earnings between £12,570 and £50,270 and 2% above that, calculated separately from your PAYE code.9GOV.UK. Rates and Thresholds for Employers 2026 to 2027 Student loan repayments come off earnings above your plan threshold: £26,900 for Plan 1, £29,385 for Plan 2 from April 2026, and £25,000 for Plan 5.10UK Parliament. Student Loans: Interest Rates and Repayment Thresholds FAQs
How to Check the Code and Fix It If Wrong
The quickest way to see how your code was built is HMRC’s online “Check your Income Tax” service. You’ll need a Government Gateway login, which you can set up if you don’t already have one.11GOV.UK. Check Your Income Tax for the Current Year Once signed in you can see each item that reduced your allowance.
If something is wrong, update it through the same service. Common corrections: a benefit you no longer receive, an out-of-date income estimate, or a professional subscription you haven’t claimed. HMRC recalculates your code, sends you a P2 Notice of Coding confirming the new figure, and pushes the update to your employer electronically.
Have these to hand when you review:
- Your P60, showing total pay and tax deducted for the year12GOV.UK. Your P45, P60 and P11D Form
- Your P11D, listing the taxable value of any employer benefits13GOV.UK. Expenses and Benefits for Employers
- Recent payslips, so you can see the current code and cumulative deductions
If Self Assessment is your only route for paying income tax, you can’t use the online tax code service and will handle it through your return instead.11GOV.UK. Check Your Income Tax for the Current Year
Scottish taxpayers see an S prefix on the code (S978L), because Scotland sets its own income tax rates. Scottish rates for 2026/27 run from 19% at the starter band up to 48% on income above £125,140, across six bands.14Scottish Government. Scottish Income Tax 2026 to 2027: Technical Factsheet
If You Overpaid or Underpaid Tax
If the 978L code was wrong and you paid too much, you have four years from the end of the tax year in which the overpayment happened to claim back the difference. An overpayment in 2025/26 must be claimed by 5 April 2030. Miss that and the refund is gone. Check sooner rather than later, because many people don’t realise their code was wrong until several years have passed.
Underpayments work the other way. HMRC charges interest on tax paid late at 7.75% a year as of January 2026, a rate set at the Bank of England base rate plus 4% and moving with it.15GOV.UK. HMRC Interest Rates for Late and Early Payments
Penalties are separate. HMRC can charge a penalty if you knew your code was wrong and didn’t tell them, especially where the error caused an underpayment. The size depends on whether the failure was deliberate and whether you came forward before HMRC found the problem; voluntary disclosure results in a lower penalty than being caught.16HM Revenue & Customs. Compliance Checks — Penalties for Failure to Notify — CC/FS11 A genuine reason for not notifying, such as serious illness, avoids a penalty as long as you act without unreasonable delay once the reason no longer applies.