RTI on every payment. Scottish rates. IR35. UK payroll, owned.
UK payroll is not a tax table exercise. It demands a live RTI submission engine, IR35 contractor status infrastructure, Scottish rate differentiation, auto-enrolment pension banding, and in-country people with direct HMRC authority relationships. Most providers configure one or two of these. Mercans delivers all of them — on a single proprietary stack with no intermediaries.
native payroll
vs nearest peer
since inception
- Employer NIC
- 15% (above £5,000/yr)
- Employee NIC
- 8% (£12,570–£50,270)
- Employee NIC (Upper)
- 2% above £50,270
- NIC Payment Deadline
- 19th / 22nd of next month
- Income Tax · Basic
- 20%
- Income Tax · Higher
- 40%
- Income Tax · Top
- 45% above £125,140
- Personal Allowance
- £12,570 / year
- Scottish Top Rate
- 48% above £125,140
- Auto-Enrolment (Employer)
- 3% min on qualifying earnings
- Auto-Enrolment (Employee)
- 5% min on qualifying earnings
- National Living Wage
- £12.21 / hr (21+)
- RTI Submission
- On or before each pay date
- P60 Deadline
- 31 May
- P11D Deadline
- 6 July
Payroll compliance: the details that can’t be missed
HMRC’s compliance infrastructure is automated and penalty-first. RTI late filings attract automatic in-year penalties from month one. IR35 assessments that reach the wrong conclusion create retrospective NIC and income tax liability for the fee-payer. The Pensions Regulator issues escalating daily fines for auto-enrolment gaps. The April 2025 NIC rate and threshold change caught dozens of payroll engines under-remitting from their first post-April payroll. None of these failures announce themselves – they compound silently until HMRC or TPR contacts you.
RTI late filing – automatic in-year penalties
Every Full Payment Submission must reach HMRC on or before the pay date. Late submissions attract automatic penalties of £100–£400 per month depending on headcount, with tax-geared penalties for persistent failure. There is no warning notice – the penalty accrues immediately.
IR35 misclassification – full fee-payer liability
Since April 2021, medium and large employers determine IR35 status for contractors. An incorrect ‘outside IR35’ determination makes the fee-payer liable for the full income tax and NIC shortfall – retroactively across the entire engagement period, plus interest from the original due dates.
April 2025 NIC – rate increase and lower threshold
From 6 April 2025, employer NIC rose from 13.8% to 15% and the secondary threshold dropped from £9,100 to £5,000/year. Payroll engines not updated by 6 April under-remit from the first post-April payroll – a cumulative shortfall HMRC recovers with interest.
Auto-enrolment non-compliance – TPR escalating fines
The Pensions Regulator issues fixed penalty notices (£400) for missed enrolment deadlines, escalating to daily penalties of £50–£10,000/day depending on workforce size. Re-enrolment every three years is a separate mandatory cycle with its own Declaration of Compliance deadline.
The three types of providers who struggle with United Kingdom
Global Aggregator Platforms
Platforms like Deel, Remote, and Rippling operate through partner networks in the UK — they don’t own the PAYE scheme, don’t manage RTI submissions directly, and don’t control the IR35 assessment workflow. When HMRC changes rates — the April 2025 NIC increase, for instance — the update travels: platform → partner → your payroll. Each handoff introduces delay and under-remittance risk.
- ×No direct HMRC PAYE scheme relationship — third-party intermediary manages filings
- ×IR35 status assessments typically absent or client-responsibility
- ×Scottish rate differentiation often not modelled natively
- ×Regulatory updates filtered through partner SLAs, not live
Large Global Payroll Incumbents
ADP, Ceridian, and similar incumbents have UK coverage — in name. In practice, their UK engines are often built on legacy architecture that wasn’t designed for UK-specific requirements: real-time RTI per payment event, Scottish income tax rate differentiation, IR35 off-payroll working logic, or the April 2025 NIC structural changes.
- ×RTI often filed in batch rather than per pay event — creating compliance timing gaps
- ×Scottish income tax rates require manual override in many legacy systems
- ×April 2025 NIC changes required manual reconfiguration in most platforms
- ×Apprenticeship Levy pay bill calculation often excludes non-payroll NIC-liable remuneration
Local UK Payroll Bureaux
Local UK payroll bureaux know the market — but they can’t scale with you. No proprietary payroll technology platform, no HCM integration, no multi-country consolidation, and no data security certifications that multinationals require. Fine for 50 employees in one entity. Inadequate for a 500-person UK operation inside a global enterprise.
- ×No proprietary payroll technology — typically Sage, Xero, or BrightPay
- ×No HCM connector — Workday, SAP, Oracle feeds require custom work
- ×No data security certifications (SOC 1/2, ISO 27701, BCR)
- ×No multi-country consolidation — cannot report across UK + European entities
The only provider that closes every gap
Mercans is the only UK payroll provider that combines a proprietary payroll technology stack, full-time in-country compliance teams, direct HMRC scheme relationships, and enterprise-grade data security — simultaneously, on one contract, with no intermediaries.
The only engine built for the UK’s actual payroll architecture
G2N Nova™ is the world’s only API-first gross-to-net payroll engine. It natively models PAYE income tax bands, employer and employee NIC as separate calculation layers with independent thresholds, Scottish and Welsh rate differentiation, auto-enrolment qualifying earnings banding, and RTI Full Payment Submission generation on every pay event. This isn’t configuration. It’s engineering.
Full-time UK team – not a partner you phone when things break
Mercans employs full-time payroll and compliance professionals in the UK. They maintain active relationships with HMRC and The Pensions Regulator – not through a contact directory, but through ongoing regulatory engagement. When HMRC issues a PAYE update, when TPR changes auto-enrolment bands, when the Chancellor announces a NIC rate change – we know before it reaches your inbox.
The security posture multinationals require – and UK GDPR mandates
UK GDPR and the Data Protection Act 2018 require payroll processors handling employee personal data to maintain documented privacy controls and data processor agreements. Mercans holds BCR approval, ISO 27701 certification, SOC 1 & 2 certifications, and ISO 27017/27018 – the only payroll provider with this complete certification stack active in the UK. Zero security breaches since inception.
Where Mercans wins on every UK-specific capability
Each row is a UK-specific capability. Each cell shows native coverage as a fill bar — full = native in-platform, half = partial / manual workaround, empty = gap.
UK Capability Coverage · 11 dimensions
HMRC real-time submission
15% / £5,000 secondary
S-code auto-applied
SDS · fee-payer NIC
£6,240–£50,270 banding
Workday · SAP · Oracle
Every rate. Every cap. Every obligation.
UK payroll operates on exact figures with hard statutory deadlines set by HMRC and The Pensions Regulator. Mercans builds every rate, threshold, and date below into G2N Nova™ and monitors them proactively – so you’re never discovering a rate change from an HMRC penalty notice.
United Kingdom · Rate & Compliance Dashboard
Live 2025–26April 2025 NIC – Double Impact of Rate Increase and Lower Threshold
From 6 April 2025, employer Class 1 NIC increased from 13.8% to 15% and the secondary threshold dropped from £9,100 to £5,000 per year. The Employment Allowance increased to £10,500 but applies only to eligible employers. Payroll engines not updated before April’s first pay date under-remit from the very first post-April payroll and create a cumulative shortfall.
→ Applied on 6 April · G2N Nova™RTI Full Payment Submission Is Per Pay Event, Not Monthly
HMRC’s RTI requires a Full Payment Submission (FPS) for every payment to every employee on or before the payment date. A single late or missed FPS triggers an automatic in-year penalty with no grace period. Monthly batch filing after payroll processing is non-compliant regardless of whether the total figures are correct.
→ Per-event RTI FPS · G2N Nova™UK GDPR and DPA 2018 Impose Specific Obligations on Payroll Processors
Processing employee payroll data in the UK requires a documented lawful basis, a Data Processing Agreement with every processor, and compliance with UK GDPR data subject rights. Post-Brexit UK GDPR is a distinct legal regime from EU GDPR. Mercans operates under BCR-approved frameworks covering both UK and EU data transfers as standard.
→ BCR · ISO 27701 · UK GDPR DPA standardAuto-Enrolment Re-enrolment Is a Separate Tri-Annual Obligation
Every three years, employers must re-enrol all eligible employees who previously opted out or ceased active membership. Re-enrolment has its own Declaration of Compliance deadline with The Pensions Regulator. Missing the re-enrolment window triggers escalating daily fines from TPR, independent of whether the original enrolment was fully compliant.
→ Re-enrolment cycle & TPR Declaration managed by MercansRun a UK payroll. Right here, right now.
Switch worker type. Move the sliders. Every number you see is the same calculation G2N Nova™ runs in production – PAYE tax code logic, NIC on the correct thresholds, auto-enrolment qualifying earnings banding, and true cost of employment exposed live.
UK Payroll Sample · Live
G2N Nova™ engineEight things only UK experts know to handle
These are the compliance details that don’t appear in standard payroll setup guides – but appear in every HMRC employer compliance review, IR35 enquiry, and TPR audit we’ve encountered in the UK over 20 years.
RTI Must Be Filed On or Before Each Pay Date – Not Monthly in Batch
HMRC’s Real Time Information system requires a Full Payment Submission for every pay event on or before the payment date. A monthly payroll with different employees paid on different dates requires multiple FPS per month. Filing in batch after the event – even on the same day – creates automatic in-year filing penalties that accumulate from month one with no prior warning.
April 2025 Changed Both the Rate and the Threshold Simultaneously
From 6 April 2025, employer NIC increased from 13.8% to 15% and the secondary threshold dropped from £9,100 to £5,000 per year. This is a double cost impact: higher rate on a wider pay base. The Employment Allowance increased to £10,500 but is only available to eligible employers with a NIC bill below £100,000 in the prior year. Engines not updated by 6 April under-remit from the first post-April payroll.
Scottish Taxpayers Pay Different Income Tax Rates Across Six Bands
Scotland has six income tax bands set by the Scottish Parliament – Starter 19%, Basic 20%, Intermediate 21%, Higher 42%, Advanced 45%, Top 48% – distinct from the three UK-wide bands. Employees with an S prefix tax code must have Scottish rates applied. Applying UK rates to Scottish employees is a direct compliance failure, and the gap between Scottish and UK rates is widening every year.
Medium and Large Employers Bear the IR35 Determination Liability
Since April 2021, medium and large businesses must assess whether each contractor engagement falls inside IR35 and issue a Status Determination Statement before the engagement starts. An incorrect ‘outside IR35’ determination shifts the full income tax and NIC liability – both employee and employer share – retroactively to the fee-payer for the entire engagement period.
Auto-enrolment Contributions Apply to Qualifying Earnings, Not Total Salary
Pension contributions under auto-enrolment are calculated on qualifying earnings between £6,240 and £50,270 per year – not on total gross salary. Computing on total salary over-contributes and distorts net pay. The trigger threshold (£10,000) and qualifying earnings band are revised annually, and re-enrolment of opted-out employees every three years is a separate mandatory cycle.
P6 Tax Code Changes from HMRC Must Be Applied in the Same Pay Period
HMRC issues P6 tax code change notices continuously throughout the tax year. Employers must implement the new code in the same pay period they receive the notice – not the following month. Emergency codes (W1/M1), cumulative adjustments, and the personal allowance taper above £100,000 (reducing by £1 for every £2 of income) all require different calculation logic. Delaying application creates over- or under-withholding that employees dispute.
Benefits in Kind Must Be Reported on P11D or Formally Payrolled – Not Ignored
Non-cash benefits – company car, private health insurance, interest-free loans above £10,000 – are taxable and subject to Class 1A NIC at 15.05%. Employers choose to report annually on P11D (by 6 July) or register to payroll benefits before the tax year begins. Switching mid-year without deregistering creates duplicate NIC payments. Many employers unknowingly run both systems simultaneously.
Apprenticeship Levy Pay Bill Includes More Than Just Processed Payroll
Employers with an annual pay bill over £3 million pay 0.5% Apprenticeship Levy on the entire pay bill minus a £15,000 allowance. The pay bill includes all remuneration subject to Class 1 NIC – not just salary on the payroll run. Benefits in kind subject to NIC, irregular bonuses, and agency workers where the employer is the secondary contributor are all in scope. Excluding any of these under-contributes to HMRC.
One workforce. Two entirely different compliance tracks.
The foundational split in UK payroll – PAYE employees on full NIC and income tax versus contractors assessed under IR35 – is not a configuration toggle. It requires separate calculation engines, different RTI treatment, and different liability frameworks depending on the IR35 determination outcome. Mercans runs both simultaneously on every pay cycle.
Parallel Compliance Engines
PAYE income tax withheld at source via tax code. Employer applies the code issued by HMRC: cumulative (adjusting each period for year-to-date position) or non-cumulative W1/M1 emergency basis. P6 tax code change notices must be applied in the same pay period received – not the following month.
Employer NIC is 15% above the £5,000 secondary threshold. From April 2025, the combined rate and threshold change means employer NIC applies on a wider base at a higher rate. Employment Allowance (£10,500) offsets part of the cost for eligible employers. NIC is paid to HMRC by the 19th (22nd electronic) of the following month.
Auto-enrolment applies to all eligible workers from day one. Employer minimum 3% plus employee minimum 5% on qualifying earnings (£6,240–£50,270). Workers who opt out must be re-enrolled every three years. Every new eligible worker must be enrolled within six weeks of the first pay date.
Statutory payments are employer obligations, partially recoverable. SSP (£116.75/week), SMP (90% AWE for 6 weeks then £184.03/week for up to 33 weeks), and SPP (£184.03/week) must be funded by the employer. SMP is recoverable at 92% from HMRC – 103% for small employers. Missing the payment is a direct employee debt.
IR35 status must be determined before engagement begins. Medium and large businesses must issue a Status Determination Statement (SDS) to the contractor before work starts. The SDS must reflect a genuine assessment of working arrangements – not a blanket ‘outside IR35’ position applied across all contractors.
Inside IR35 means full PAYE and NIC liability falls on the fee-payer. Where a contractor is determined inside IR35, the business paying them must deduct income tax and employee NIC and pay employer NIC at 15%, as if the contractor were a direct employee. The contractor’s personal service company is not responsible.
A wrong determination is retrospective and interest-bearing. HMRC can challenge IR35 determinations years after the engagement ends. A successful challenge assigns the full tax and NIC shortfall for the entire period to the fee-payer, plus interest from the original payment due dates.
Agency workers introduce a different secondary NIC chain. Where a worker is supplied via an agency, the secondary NIC liability sits with the entity in the supply chain that pays the worker. Identifying the correct secondary contributor is a structural payroll question that must be resolved before the first payment.
Every obligation. Every authority. Mercans owns the calendar.
UK compliance runs across HMRC, The Pensions Regulator, and the ICO on per-event, monthly, and annual cadences. Mercans’ managed payroll absorbs every filing as standard scope — you don’t track deadlines. We do.
RTI Full Payment Submission (FPS)
A Full Payment Submission filed with HMRC on or before each employee payment date. Contains gross pay, tax, NIC, and year-to-date figures for every employee paid. Late or missing FPS triggers automatic in-year filing penalties with no warning notice. No batching permitted – each payment event requires its own FPS.
PAYE & NIC Payment to HMRC
Combined PAYE income tax and Class 1 NIC (employer 15% + employee 8%) paid to HMRC by the 19th of the following month (22nd electronic). Late payment attracts surcharges from 1% for 1–3 days late, rising to 15% for persistent late payment. The Employment Allowance (£10,500) is claimed via the Employer Payment Summary.
Auto-Enrolment Pension Contributions
Employer minimum 3% and employee minimum 5% contributions on qualifying earnings (£6,240–£50,270) remitted to the pension provider within the contribution payment deadline. Contributions must be paid into the scheme – not just deducted from payroll. TPR enforces contribution deadlines independently from HMRC.
P60 – Annual Earnings and Tax Certificate
P60 issued to every employee employed on 5 April (the last day of the tax year). Shows total pay and tax deducted for the full year. Used by employees to reconcile self-assessment returns. Failure to issue by 31 May is a compliance failure. Electronic P60s are permitted if employees can print them.
P11D – Benefits in Kind Report
P11D filed with HMRC detailing all taxable benefits provided to each employee – company car, private health insurance, loans above £10,000. Class 1A NIC at 15.05% on the total taxable value paid by 19/22 July via P11D(b). Employers registered to payroll benefits before the tax year do not file P11D.
New Tax Year – Rates, Thresholds and Codes Reset
The UK tax year runs 6 April to 5 April. On 6 April, new NIC rates and thresholds, income tax bands, National Living Wage rates, and auto-enrolment qualifying earnings limits take effect. The first payroll of the new year must also reset cumulative PAYE year-to-date calculations for every employee.
P45 – Employee Leaver Document
P45 issued to every employee on leaving, detailing cumulative pay and tax withheld to date in the tax year. Filed with HMRC via the RTI system. Failure to issue means the next employer applies emergency tax code W1/M1, over-withholding from the employee until their tax position is corrected.
Auto-Enrolment Re-enrolment & TPR Declaration
Every three years, all eligible employees who opted out or ceased active membership must be re-enrolled into the workplace pension. A Declaration of Compliance must be submitted to TPR within five months of the re-enrolment date. Failure triggers escalating fixed and daily penalty notices from TPR.
UK is one market. Mercans covers all of Europe.
For companies running payroll across multiple European markets, complexity multiplies – not adds. Each country runs its own tax authority, social security body, and employment law framework. Mercans covers all major European markets on a single platform with country-specific compliance engines running in parallel.
covered
1 contract
consolidation
European
Every filing. Every format. Submission-ready.
Mercans generates the exact file types that HMRC, The Pensions Regulator, and the ICO expect to receive — not formatted summaries that need reformatting before submission.
