Setting up payroll for the first time feels like learning a new language. PAYE, RTI, NI thresholds, it’s a lot. But once you break it down, it’s just a repeatable monthly process HMRC uses to collect Income Tax and National Insurance directly from wages.
From registering as an employer to operating PAYE, submitting Real Time Information(RTI), and ensuring pension compliance, payroll is not just an administrative task–it is an ongoing legal responsibility. When handled incorrectly, even small payroll errors can result in penalties, employee dissatisfaction, and avoidable cash flow pressure.
AT RMA Accountants, we regularly support businesses that started with simple payroll needs but quickly found the system more complex than expected. This guide breaks down payroll setup and the PAYE system in a clear, practical way so UK employers can stay compliant from day one.
Why Payroll Compliance Is Critical For UK Employers
PAYE (Pay As You Earn)is HMRC’s system for collecting income tax and National Insurance directly from employee earnings before wages are paid. In simple terms, employers act as the operating point between HMRC and employees.
Employers must ensure:
- Employees are paid accurately and on time
- Correct income tax is deducted under HMRC tax codes
- National Insurance contributions are calculated correctly
- Employer NIC liabilities accounted for
- Payroll reports are submitted through RTI
- Payments to HMRC are made within deadlines
- Statutory obligations such as pensions are fulfilled
From a compliance perspective, payroll is not an optional function. It is monitored continuously by HMRC through real-time reporting, meaning errors are identified far more quickly than in traditional annual systems.
Step One: Register As An Employer With HMRC
Before any payroll activity begins, a business must register as an employer with HMRC. This step is often underestimated, particularly by first-time employers.
Registration is required if you are:
- Paying an employee at or above the HMRC earning thresholds
- Hiring someone with another job and pension income
- Providing taxable benefits or expenses
- Operating a limited company paying director salaries
Once registered, HMRC issues:
- A PAYE reference number
- An Accounts Office reference number
All of this information is important for payroll reporting and HMRC payments.
Step Two: Setting Up A Reliable Payroll System
HMRC requires employers to maintain digital payroll records and submit data electronically using Real Time Information(RTI). This makes payroll software a necessity rather than a choice.
A properly structured payroll system should support:
- Automated PAYE and NIC calculation
- Accurate payslip generation
- RTI submissions (FPS and EPS)
- Statutory pay processing (SSP, SMP, SPP)
- Pension deduction tracking
- Secure record retention
HMRC’s Basic PAYE Tools may be sufficient for very small employers, but as payroll complexity increases, most businesses benefit from dedicated payroll software or outsourced payroll services.
From experience, businesses that invest in the right payroll system early reduce long-term compliance risks significantly.
Step Three: Collect Employee Details Before First Payday
Payroll accuracy depends entirely on the quality of the employees data collected at the onboarding stage.
Employers must obtain:
- Full legal name and date of birth
- National Insurance number
- Home address and contact detail
- Start date and employment terms
- Salary or hourly rate
- Tax code (From P45 or HMRC starter checklist)
Where a P45 is unavailable, the HMRC starter checklist ensures the correct emergency tax code is applied until HMRC updates the employee record.
Incorrect or incomplete employee data is not a minor administrative issue—it is one of the leading causes of payroll discrepancies, tax mismatches, and correction services from HMRC.
Step Four: Understanding PAYE Deductions in Practice
Once payroll is active, employers must correctly calculate the statutory deduction for each pay period.
Income Tax
Income Tax is applied based on HMRC-issued tax codes. The most commonly used code for standard employees is 1257L, which reflects the personal allowance.
However, Tax codes may be adjusted due to:
- Multiple sources of income
- Benefits in kind (company cars, healthcare, etc.)
- Previous underpaid tax
- HMRC compliance adjustments
Applying the wrong tax code can lead to cumulative errors that often take months to correct through HMRC reconciliation.
National Insurance Contribution
National Insurance is calculated based on earnings thresholds and employee category letters assigned by HMRC.
Employers are responsible for:
- Deduction employee NICs correctly
- Paying employee NIC contributions
- Applying the correct category letter
A common issue we see in practice is incorrect category allocation, particularly for directors or employees with variable earnings, which can distort payroll liabilities.
Step Five: Real Time Information(RTI) Reporting
HMRC operates payroll through Real Time Information(RTI), meaning data must be submitted every time employees are paid.
Full Payment Submission (FPS)
The FPS is the core payroll submission and must be sent:
- On or before each employee’s payday
It includes:
- Gross pay
- Tax and NIC deduction
- Pension contributions
- Statutory payments
Late submissions are a common trigger for HMRC penalties, particularly for businesses running payroll manually or without automation.
Employer’s Payment Summary (EPS)
An EPS is used to report adjustments such as:
- Employment Allowance claims
- Statutory payment recoveries
- Periods with no employee payments
This ensures HMRC records remain aligned with actual employer liabilities.
Step Six: Paying HMRC Accurately And On Time
Once RTI submissions are complete, employers must pay HMRC the total PAYE liability.
This typically includes:
- Income Tax
- Employee National Insurance
- Student loan deduction
- Apprenticeship levy (if applicable)
Payment deadlines are:
- 22nd of the month for electronic payments
- 19th of the month for postal payments
From a cash flow perspective, many businesses underestimate the timing gap between payroll process and HMRC payment deadlines, which can create pressure if not planned in advance.
Common Payroll Mistakes That Trigger Penalties
In our experience working with UK businesses, payroll issues usually arise from process gaps rather than intent.
The most frequent errors include:
- Late or missed RTI submissions
- Incorrect tax code application
- National Insurance category mistakes
- Failure to update employee changes promptly
- Inaccurate onboarding data
- Weak payroll record management
Employers are legally required to retain payroll records for at least three tax years, although maintaining longer records is often advisable for audit readiness.
The Value Of Professional Payroll Support
Payroll legislation is not static. HMRC thresholds, tax code, and reporting requirements change regularly, often with limited transition periods.
Professional payroll support ensures:
- Continuous HMRC compliance
- Accurate and timely submissions
- Reduced administrative burden
- Proper handling of complex payroll corrections
- Reduced risk of penalties and corrections
Outsourcing payroll is not just about convenience—it is about ensuring financial accuracy and compliance consistency across the business.
Conclusion
At the end of the day, payroll isn’t just about paying people. It’s a key part of tax planning. It’s about making sure your team gets paid correctly and on time, while you stay on the right side of HMRC without losing sleep over it.
Register early, handle the calculations, submit your FPS before payday, and keep your records tidy. Once that’s running smoothly, you can shift your focus from firefighting to the bigger picture: using payroll as part of your tax planning, cutting unnecessary costs, and keeping more of what you earn legally.
If it feels like too much admin, that’s what accountants like RMA are for. You don’t have to do it all alone. Having someone who knows the rules and keeps an eye on changes means you get peace of mind and more time to actually run your business.
