Introduction
Did you know that UK businesses paid over £50 million in HMRC payroll penalties last year? That’s not a typo – fifty million pounds in completely avoidable fines.
As a Chartered Accountant working with small businesses across Edinburgh and beyond, I see the same payroll mistakes repeated time and time again. The frustrating part? Most business owners don’t even realize they’re making these errors until that dreaded brown envelope from HMRC lands on their doormat.
Whether you’re running your first payroll for a newly hired employee or managing a team of ten, the rules are the same – and HMRC doesn’t offer grace periods for “not knowing.” The good news? Once you understand these three critical mistakes, you can avoid them entirely and keep your hard-earned money where it belongs: in your business.
Let’s dive into the three biggest payroll mistakes that could be costing you thousands, and more importantly, how to fix them.
Mistake #1: Missing Real Time Information (RTI) Deadlines
What is RTI and Why Does It Matter?
Real Time Information (RTI) is HMRC’s system for collecting payroll information from employers. Every time you run payroll, you must submit a Full Payment Submission (FPS) to HMRC telling them exactly what you’ve paid your employees and how much tax and National Insurance you’ve deducted.
The critical rule that trips up most business owners? Your FPS must be submitted on or before the day you pay your employees. Not the day after. Not when you get around to it. Not at the end of the week. On or before payday.
The True Cost of Being Late
Miss that deadline, and HMRC’s automatic penalty system kicks in immediately:
• First late submission in a tax year: Warning letter (no fine, but you’re now on their radar)
• Subsequent late submissions: £100 to £400 per month, depending on how many employees you have
• Multiple late submissions: Penalties escalate quarterly
Here’s a real-world example: A small café with 5 employees consistently submits their FPS 2-3 days late each month. They receive a £100 monthly penalty. Over 12 months, that’s £1,200 in penalties for literally no reason other than poor timing.
For larger employers (50+ employees), monthly penalties can reach £400. That’s £4,800 per year thrown away on late submissions.
How RTI Catches People Out
The confusion often stems from how businesses handle their payroll process. Many business owners follow this pattern:
- Friday: Pay employees via bank transfer
- Weekend: Relax, job done!
- Monday or Tuesday: Log into payroll software and submit FPS
- Following week: Penalty notice arrives
They assume submitting “close to” payday is acceptable. It’s not. HMRC’s systems are automated and unforgiving.
How to Avoid RTI Penalties
Set up your process correctly from day one: - Process your payroll BEFORE you pay employees – Run all calculations at least 24 hours before payday
- Submit your FPS immediately – As soon as payroll is processed, submit the FPS to HMRC
- Verify submission – Check your payroll software confirms successful HMRC receipt
- Only then pay your employees – Transfer wages after FPS is safely submitted
Pro tip: If you pay employees on the last Friday of the month, process your payroll on Thursday. Submit your FPS Thursday evening. Pay employees Friday morning. This buffer protects you from technical glitches or bank holidays.
Use technology wisely: Modern payroll software like BrightPay, Xero Payroll, or Sage automatically submits RTI for you – but only if you complete the payroll run on time. Set calendar reminders 48 hours before each payday to trigger your payroll process.
What if you’ve already missed a deadline? Submit immediately. While you’ll likely receive a penalty for the missed deadline, submitting late is better than not submitting at all. Continued non-submission leads to daily penalties of up to £10,000.
Mistake #2: Using Incorrect or Outdated Tax Codes
Why Tax Codes Matter More Than You Think
Your employee’s tax code tells you exactly how much income tax to deduct from their wages. Get it wrong, and one of two things happens:
- You deduct too little tax – Your employee faces an unexpected tax bill at year-end, and they’ll blame you
- You deduct too much tax – Your employee is effectively lending money to HMRC interest-free, and again, they’ll blame you
Either scenario damages your relationship with your employee and could expose you to penalties if HMRC determines you should have known the code was incorrect.
How Tax Codes Get Out of Date
Tax codes change more frequently than most people realize. HMRC updates tax codes when:
• An employee starts receiving company benefits (car, medical insurance, etc.)
• They begin or stop receiving state benefits or pensions
• They have multiple jobs and their tax-free allowance needs redistributing
• They’ve overpaid or underpaid tax in previous years
• Their personal circumstances change (marriage, civil partnership, etc.)
HMRC sends tax code updates electronically to employers, but here’s where it goes wrong: If you’re not checking your payroll software regularly, you might miss these updates entirely.
The Real-World Impact
Consider Sarah, who runs a small marketing agency with 8 employees. One employee, Tom, started receiving a company car in April. HMRC updated his tax code from 1257L to 1057K to account for the benefit-in-kind.
Sarah’s payroll software received the update, but she didn’t notice the notification. For six months, Tom was taxed on the old code, underpaying approximately £150 per month. Come October, HMRC sent Tom a letter demanding £900 in unpaid tax.
Tom was furious with Sarah. The agency had to handle an upset employee, explain a complex tax situation, and deal with damage to their professional relationship. Sarah also faced a formal query from HMRC about why the incorrect code was used for so long.
Emergency Tax Codes: A Common Trap
The most problematic tax codes are emergency ones: BR, D0, and D1.
• BR (Basic Rate): Taxes all income at 20% with no tax-free allowance
• D0: Taxes all income at 40%
• D1: Taxes all income at 45%
These codes apply when HMRC doesn’t have enough information about an employee – typically new starters who haven’t provided a P45 from their previous employer.
Emergency codes are meant to be temporary – usually just the first month or two of employment until proper information is received. Yet I regularly see businesses still using emergency codes 6, 8, or even 12 months into someone’s employment. This means the employee has been massively overtaxed and will need to claim a refund from HMRC.
How to Avoid Tax Code Mistakes - Check for updates weekly Log into your payroll software every week and check for HMRC notifications. Most software has a notifications or messages section specifically for tax code updates.
- Act on updates immediately When you receive a new tax code, apply it from the date specified by HMRC. Don’t wait until next month’s payroll.
- Verify emergency codes monthly If any employee is on BR, D0, or D1, check why. Have they provided their P45? Have you submitted their starter checklist to HMRC? Follow up until they’re on a proper cumulative code (usually ending in L, M, or N).
- Reconcile at year-end Before submitting P60s in April, verify every employee’s tax code is correct. This is your last chance to catch and correct errors before they become HMRC’s problem.
- Communicate with employees When a tax code changes, tell your employee. A simple email saying “HMRC has updated your tax code from X to Y, which will affect your take-home pay by approximately £Z” prevents confusion and shows professionalism.
What if you discover you’ve been using the wrong code? Contact HMRC immediately through the Employer Helpline (0300 200 3200). They can advise on correcting past errors and issuing amended payslips. The sooner you address it, the less complicated the fix.
Mistake #3: Ignoring Auto-Enrolment Pension Duties
The Biggest Misconception About Auto-Enrolment
Here’s what I hear constantly: “But I only have one employee, surely auto-enrolment doesn’t apply to me?”
Let me be crystal clear: Every UK employer must comply with auto-enrolment pension duties. Every. Single. One.
It doesn’t matter if you employ one person or one hundred. It doesn’t matter if your employee is your cousin who works Saturdays. It doesn’t matter if they’ve told you they don’t want a pension. The legal duty sits with you as the employer, and it’s non-negotiable.
What Auto-Enrolment Actually Means
Auto-enrolment requires you to:
- Assess every worker – Determine if they’re an eligible jobholder, non-eligible jobholder, or entitled worker
- Automatically enrol eligible workers – Put them into a qualifying pension scheme without asking their permission
- Pay minimum contributions – Currently 3% of qualifying earnings as the employer, with the employee contributing at least 5%
- Allow opt-outs – Employees can choose to leave the scheme, but you cannot encourage or suggest they do so
- Re-enrol every three years – Workers who opted out must be put back in the scheme
- Keep detailed records – Maintain evidence of assessments, enrolments, and communications for six years
Who Needs to Be Auto-Enrolled?
An eligible jobholder is any worker who:
• Is aged between 22 and State Pension age
• Earns more than £10,000 per year (£833 per month)
• Works in the UK
If your employee meets all three criteria, you must enrol them. You don’t ask if they want it. You don’t discuss it. You automatically enrol them, then inform them of their right to opt out.
The Penalties Are Eye-Watering
The Pensions Regulator doesn’t mess around. Here’s their penalty structure:
Stage 1: Fixed Penalty Notice
• £400 for failing to comply with auto-enrolment duties by your staging date
Stage 2: Escalating Penalty Notice If you continue to ignore your duties after the fixed penalty:
• £50 per day for employers with 1-4 workers
• £500 per day for employers with 5-49 workers
• £2,500 per day for employers with 50-249 workers
• £10,000 per day for employers with 250+ workers
Yes, you read that correctly. Per day. These penalties continue until you comply.
Let me give you a real example: A small business with 3 employees ignored their staging date letter from The Pensions Regulator. They received a £400 fixed penalty. They still didn’t act, assuming it was a mistake because they were “too small.”
The Pensions Regulator issued an escalating penalty of £50 per day. By the time the business owner finally sought help (after receiving a letter threatening court action), they owed £7,150 in penalties. That’s £400 fixed penalty plus £6,750 in daily penalties (135 days x £50).
For a micro-business, that’s devastating.
Common Auto-Enrolment Myths Debunked
Myth 1: “My employee already has a pension, so I don’t need to do anything” Reality: You still must assess them and auto-enrol them into YOUR scheme if they’re eligible. Their personal pension is irrelevant.
Myth 2: “My employee said they don’t want a pension” Reality: You cannot ask them before enrolment. You must auto-enrol them first, then they can opt out if they choose.
Myth 3: “I’ll set up a pension when I get around to it” Reality: You have legal duties from your staging date (set by The Pensions Regulator based on when you became an employer). There’s no flexibility.
Myth 4: “Surely they won’t penalize a small business” Reality: The Pensions Regulator’s automated systems don’t distinguish between a sole trader with one employee and a corporation with thousands. The law is the law.
Myth 5: “I can’t afford employer contributions” Reality: Employer contributions are a legal employment cost, like paying National Insurance. If you can’t afford them, you legally cannot employ that person.
How to Get Auto-Enrolment Right - Know your staging date If you’re a new employer, your staging date is typically the day you first pay someone £533 or more in a month. You can check your specific staging date at www.thepensionsregulator.gov.uk/staging-date
- Choose a qualifying pension scheme Popular options for small employers include:
• NEST (National Employment Savings Trust) – government-backed, very low fees
• The People’s Pension – simple, good for micro-businesses
• NOW: Pensions – straightforward setup
• Standard Life – if you want more investment options - Assess your workers For each person on your payroll, determine their category:
• Eligible jobholder: Age 22-State Pension age, earning £10,000+ = Must be auto-enrolled
• Non-eligible jobholder: Age 16-21 or State Pension age-74, earning £6,240-£10,000 = Have right to opt in
• Entitled worker: Earning under £6,240 = Have right to join - Complete your declaration of compliance Within 5 months of your staging date, you must complete a declaration on The Pensions Regulator’s website confirming you’ve met your duties. This is non-negotiable.
- Maintain ongoing compliance
• Re-assess workers annually (in case their age or earnings change)
• Re-enrol opted-out workers every 3 years
• Keep records for 6 years
• Respond to Pensions Regulator queries promptly - Integrate with payroll Most modern payroll software (Xero, BrightPay, Sage) integrates directly with pension providers. Set this up properly and contributions happen automatically each pay run.
What If You’ve Missed Your Staging Date?
Don’t panic, but do act immediately. - Set up a qualifying pension scheme today
- Enrol all eligible workers backdated to your staging date
- Calculate and pay all missed employer contributions (including backdated amounts)
- Complete your declaration of compliance
- Contact The Pensions Regulator explaining the situation
You’ll likely still receive a fixed penalty, but taking immediate action prevents escalating daily penalties and shows good faith. The Pensions Regulator is more lenient with employers who self-report and quickly rectify the situation than those who wait to be chased.
Conclusion: Knowledge is Your Best Protection
These three payroll mistakes – missing RTI deadlines, using incorrect tax codes, and ignoring auto-enrolment – cost UK businesses millions every year in entirely preventable penalties.
The common thread? Lack of knowledge and inadequate systems.
Most business owners aren’t deliberately trying to break the rules. They’re simply overwhelmed by the complexity of payroll legislation, juggling too many responsibilities, or relying on outdated information.
Here’s the truth: Payroll is complex, constantly changing, and high-stakes. One mistake can trigger penalties, damage employee relationships, and create months of administrative headaches sorting it out with HMRC.
But it doesn’t have to be this way.
Your Next Steps
If you’re currently managing payroll yourself:
- Audit your current process – Are you submitting RTI on time, every time? When did you last check tax codes? Have you completed your auto-enrolment duties?
- Set up proper systems – Calendar reminders, payroll checklists, weekly software checks. Make compliance automatic, not something you remember to do.
- Educate yourself – HMRC offers free webinars and guidance. The Pensions Regulator has excellent resources. Invest time in understanding your legal obligations.
- Know when to get help – There’s no shame in admitting payroll is outside your expertise. The cost of professional help is almost always less than HMRC penalties.
Need Expert Support?
At KAF Advisory, I specialize in taking the payroll burden off small business owners’ shoulders. Whether you need full payroll processing, a compliance audit, or just someone to answer your questions and give you peace of mind, I’m here to help.
As a Chartered Accountant (ACA ICAEW), I stay updated on every payroll legislation change so you don’t have to. My payroll services include:
✓ Full payroll processing (weekly, monthly, or custom schedules)
✓ Real Time Information submissions to HMRC
✓ Auto-enrolment pension compliance
✓ Tax code management and updates
✓ Statutory payments (SSP, SMP, SPP, SAP)
✓ Year-end reporting (P60s)
✓ HMRC correspondence handling
✓ Dedicated expert support when you have questions
Book a free 15-minute consultation to discuss your payroll situation and find out how I can help ensure you’re fully compliant while saving you time and stress.
📞 Call: 07769431533
📧 Email: contact@kafadvisory.co.uk
🌐 Visit: www.kafadvisory.co.uk
Your employees deserve to be paid correctly and on time. Your business deserves to avoid unnecessary penalties. Let’s make both happen.
About the Author:
Afusat Adebayo is a Chartered Accountant (ACA ICAEW) and founder of KAF Advisory, an accountancy practice based in Edinburgh specializing in small business support, payroll services, and tax compliance. With experience managing budgets exceeding £180 million in the public sector and supporting diverse businesses across Scotland, Afusat is passionate about making accounting accessible and understandable for entrepreneurs and small business owners.
Related Resources:
• HMRC: PAYE and payroll for employers
• The Pensions Regulator: Automatic enrolment
• HMRC Employment Status Check (CEST)
Disclaimer: This article provides general guidance on UK payroll compliance as of February 2026. Tax legislation changes regularly. For advice specific to your circumstances, please consult a qualified accountant or tax adviser.
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