Publishing a gender pay gap report without an action plan is a reputational risk. Publishing a wrong one is a compliance risk. UK employers with 250 or more employees face a mandatory annual reporting requirement under the Equality Act 2010 (Gender Pay Gap Information) Regulations 2017, with a deadline of 4 April each year for private sector and voluntary sector organisations. Understanding the six prescribed metrics, the common calculation errors that distort reported figures, and how to use the reporting process as a genuine driver for equitable compensation is what separates organisations that manage the process well from those that generate annual press coverage for the wrong reasons.
Who Must Report and When
The gender pay gap reporting obligation applies to "relevant employers" — private sector and voluntary sector organisations with 250 or more employees — as of the snapshot date of 5 April each year. Public sector organisations have a different snapshot date of 31 March. The reporting deadline is exactly 12 months after the snapshot date: 4 April for private sector employers (or 30 March for public sector).
"Employees" for the purposes of the regulations has a broader definition than simply those on the payroll. The relevant headcount includes: employees under a contract of employment; workers (those under a contract to personally perform work who are not running their own business); and partners of limited liability partnerships. Zero-hours workers count if they were paid in the pay period including the snapshot date. Agency workers provided to a business count toward the agency's headcount, not the client's — though this is a nuanced area where ACAS guidance should be consulted.
Organisations below the 250-employee threshold are not legally required to report but are encouraged to do so voluntarily. Threshold assessment is based on the snapshot date headcount, not an annual average. A company that crosses 250 employees between snapshot dates is obligated from the following reporting cycle.
Reporting Deadlines Summary
Private sector and voluntary sector: Snapshot date 5 April, reporting deadline 4 April (12 months later). Public sector authorities: Snapshot date 31 March, reporting deadline 30 March (12 months later). Reports must be published on the employer's own website (accessible without restriction) and uploaded to the government's GPG reporting service at gender-pay-gap.service.gov.uk. Both publications are mandatory — uploading to the government service alone does not satisfy the own-website requirement.
The 6 Metrics You Must Calculate and Publish
The regulations prescribe exactly six metrics that must be calculated and published. There is no discretion on which metrics to report — all six are mandatory:
- Mean gender pay gap: The difference between the mean (average) hourly pay of male and female employees, expressed as a percentage of mean male hourly pay. Formula: ((Mean male pay - Mean female pay) / Mean male pay) x 100.
- Median gender pay gap: The difference between the median hourly pay of male and female employees, expressed as a percentage of median male hourly pay. Uses the midpoint pay figure when all employees are ranked by pay from lowest to highest.
- Mean bonus pay gap: The difference between the mean bonus paid to male and female employees during the 12-month period ending with the snapshot date, as a percentage of mean male bonus pay. Includes all bonus payments: performance bonuses, profit sharing, discretionary bonuses, and long-term incentive plan (LTIP) payments when vested during the period.
- Median bonus pay gap: The difference between the median bonus paid to male and female employees during the 12-month period, as a percentage of median male bonus pay.
- Proportion of males and females receiving a bonus: The percentage of male employees and percentage of female employees who received any bonus payment during the 12-month reporting period.
- Proportion of males and females in each pay quartile: Employees are ranked by hourly pay from lowest to highest and divided into four equal-sized groups (quartiles). The proportion of male and female employees in each quartile is reported. This metric often reveals structural concentration patterns — for example, women constituting 70% of the lowest pay quartile and 20% of the highest.
What Counts as "Hourly Pay" for GPG Calculations
Hourly pay for GPG purposes is calculated from the gross pay received in the "relevant pay period" — the pay period (weekly, monthly) that includes the 5 April snapshot date. Included in ordinary pay: basic salary, paid leave, maternity/paternity pay (at full pay, not statutory rate), allowances (car, location), shift and on-call premiums, and piecework pay. Excluded: overtime (unless guaranteed), expenses, benefits in kind, salary sacrifice amounts (the salary is counted pre-sacrifice in some circumstances), redundancy pay, and pay in lieu of leave. Hourly pay is calculated by dividing the relevant pay period gross pay by the number of hours worked in that period. Part-time employees' pay must be annualised to compare on an equivalent basis — or correctly calculated on an hourly rate basis, which achieves the same result.
Mean vs Median Pay Gap: Which Number Matters More
Both mean and median gaps are legally required and both matter — but they measure different things and tell different stories about your organisation's pay structure.
The mean pay gap is sensitive to extreme values. A small number of very high earners — almost always male in most organisations — pulls the mean up and widens the reported gap. A technology company with five male executives earning £500,000+ will show a significantly higher mean gap than median gap. This means the mean gap overstates the typical experience of most employees but captures the structural inequality at the top of the organisation.
The median pay gap is the "middle" — where exactly half of employees earn more and half earn less. The median is less influenced by outliers and better represents the typical pay difference experienced by most employees. In most organisations, the median gap is smaller than the mean gap.
Neither figure is the "real" gap and the other the misleading one. The gap between them tells its own story: a large difference between mean and median typically indicates significant pay compression or outlier influence at the senior level. Reporting both numbers and explaining the dynamic between them in your narrative demonstrates analytical sophistication and transparency.
| Metric | What It Measures | Sensitive To | Use For |
|---|---|---|---|
| Mean pay gap | Average pay difference | High earner outliers | Leadership-level analysis |
| Median pay gap | Typical pay difference | Middle-distribution patterns | Workforce-wide structural analysis |
| Pay quartiles | Distribution across pay bands | Job grading and role segregation | Identifying structural concentration |
| Bonus gap (mean) | Average bonus difference | Executive-level bonus structures | Senior compensation equity |
| Bonus participation | Who receives bonuses at all | Part-time / leave exclusion patterns | Access and eligibility analysis |
Common Calculation Errors That Distort Your Gap
GPG calculation errors frequently produce reported figures that do not accurately reflect the organisation's pay data — creating compliance risk and, when errors are later identified and corrected, reputational damage. The most common errors HR teams encounter:
- Incorrect hourly rate calculation for part-time employees: Part-time employees must be included using their actual hourly rate — not an annualised equivalent or a pro-rated salary figure divided by standard full-time hours. Using full-time hours as the denominator for part-time employees understates their hourly rate and can distort the median in either direction depending on the gender distribution of part-time workers.
- Including excluded pay elements: Including overtime pay, expenses, benefits in kind, or redundancy payments in the "ordinary pay" calculation inflates hourly pay figures. These must be excluded. Overtime that is contractually guaranteed (not voluntary) may be included, but most overtime should be excluded.
- Mishandling employees on leave: Employees on reduced-rate maternity or sick pay during the relevant pay period present a specific calculation challenge. The regulations require that employees receiving full pay are included using their full pay; employees receiving reduced or nil pay are excluded from the hourly pay calculation (but included in the bonus participation calculation for the 12-month bonus period). Getting this wrong is one of the most common calculation errors.
- Using incorrect snapshot date data: The headcount and pay data must reflect the position as at the snapshot date (5 April), not month-end, not a payroll run date close to but not on 5 April. If your payroll cycle does not align with 5 April, manual calculation from actual 5 April data is required.
- Incorrectly defining the bonus reference period: The 12-month bonus period ends on the snapshot date. Bonuses paid after the snapshot date but earned during the period are included; bonuses earned before the period started but paid during it are excluded. LTIP vesting dates, not grant dates, determine which reporting period they fall into.
ACAS and Government Guidance: The Authoritative Sources
For calculation queries, the two authoritative sources are the Government Equalities Office's technical guidance ("Making your calculations" document, available on Gov.uk) and ACAS's gender pay gap reporting guidance. The government's online GPG reporting service also includes a built-in calculation tool that can validate results. Employers uncertain about specific inclusions or exclusions should consult employment solicitors with pay equality experience rather than relying on generic HR guidance.
Writing a Narrative That Holds Up to Scrutiny
The regulations require publication of the six prescribed figures. They do not legally require a written narrative — but failing to provide one is a significant missed opportunity and a reputational risk. A large pay gap published without context reads as either ignorance or evasion.
An effective narrative addresses three questions with specificity:
Why does the gap exist? The structural causes of a gender pay gap differ by organisation. Common explanations include: concentration of women in lower-pay grades or functions, concentration of men in senior and leadership roles, higher proportion of women in part-time roles, and historical pay benchmarking that has embedded historical inequities. These causes are different problems requiring different solutions. Generic explanations ("this reflects our industry structure") without supporting data hold up poorly to media and employee scrutiny.
What has already changed? Narrative credibility depends on demonstrating that the gap is not static. Reporting year-on-year movement, specific initiatives and their measured outcomes, and changes in leadership or senior team composition demonstrates active management.
What will change, by when, measured how? Commitments without metrics are not commitments. Effective action plans specify targets (e.g., "increase women in senior management from 28% to 40% by 2028"), the specific mechanisms to achieve them (mentoring programme, structured promotion processes, pay equity review), and how progress will be measured. Organisations that publish specific, measurable commitments and then report against them in subsequent years build stakeholder trust in a way that annual generic statements do not.
How to Use the Gap as a Driver for Action
The organisations that manage their gender pay gap most effectively treat the annual reporting cycle as an accountability mechanism for an ongoing compensation equity programme, not an annual compliance exercise.
Effective programmes share several characteristics:
- Pay equity analysis separate from GPG reporting: GPG reporting measures the mean and median difference between all male and female employees — it is a population-level statistic heavily influenced by representation rather than pay equity at the individual level. Pay equity analysis compares male and female pay within the same role, grade, and performance band. Both analyses are necessary. The GPG identifies structural concentration issues; pay equity analysis identifies like-for-like pay discrimination.
- Promotion rate monitoring: GPG gaps widen over time when promotion rates, performance ratings, or bonus participation differ by gender even when starting salaries are equivalent. Track promotion rates by gender at each grade annually.
- Hiring and offer data: Monitor offer salary distributions by gender for external hires at each seniority level. Patterns where male candidates receive systematically higher offers for equivalent roles are both a pay equity problem and an employment discrimination risk.
- Part-time and flexible working access: In most UK organisations, women hold a disproportionate share of part-time roles, which contributes to GPG through both lower absolute pay and reduced access to performance bonuses structured around full-time equivalents. Extending genuine flexible working access across all seniority levels, and ensuring bonus and performance frameworks apply equitably to part-time employees, addresses this systematically.
The Difference Between GPG and Equal Pay Analysis
The gender pay gap (GPG) measures the mean and median difference in pay between all male and all female employees — it reflects representation and concentration patterns across the workforce. Equal pay analysis compares pay for men and women in equivalent roles, grades, and performance bands — it identifies direct pay discrimination. Both analyses are essential for a complete pay equity programme. A company could have a significant GPG driven by occupational segregation at the top while paying men and women in equivalent roles identically, and vice versa. Treegarden's pay equity module produces both analyses from the same employee compensation data, allowing HR teams to distinguish structural issues from individual pay discrimination and target interventions appropriately.
How Treegarden's Pay Equity Reports Support GPG Compliance
Treegarden's compensation management module includes pay equity analysis and gender pay gap reporting tools designed to support both the annual regulatory reporting cycle and ongoing compensation equity management. The specific capabilities relevant to GPG compliance:
Pay equity analysis: Treegarden's pay equity reports compare compensation across employees by role, grade, and tenure, with gender-stratified views that identify like-for-like pay disparities within peer groups. This complements the top-line GPG report by enabling the deeper analysis needed to distinguish structural concentration effects from actual pay discrimination.
Pay compression analysis: Identifies situations where salary compression has eroded distinctions between pay grades — often affecting experienced female employees disproportionately when new external hires are brought in at competitive market rates that compress legacy pay structures. Understanding compression is essential for GPG action planning.
Compensation planning: Treegarden's compensation planning tools allow HR teams to model proposed pay adjustments, identify their effect on the gender pay gap, and simulate the cost and GPG impact of different remediation scenarios before implementing changes. This allows targeted investment in equity improvement rather than across-the-board adjustments.
Headcount and promotion analytics: Promotion rates, hiring volumes, and offer distribution by gender are tracked within the platform, providing the quarterly data needed to monitor progress against action plan commitments rather than discovering year-on-year movements only at reporting time.
Free Calculators for This Topic
Save time with these free HR calculators — no sign-up required:
Frequently Asked Questions
What is the Gender Pay Gap reporting deadline for 2026?
For private sector and voluntary sector employers, the snapshot date is 5 April 2025 and the reporting deadline is 4 April 2026. The report must be published on the employer's own website and uploaded to the government's GPG reporting service (gender-pay-gap.service.gov.uk) by the deadline. Public sector authorities have a snapshot date of 31 March 2025 and a reporting deadline of 30 March 2026.
What happens if an employer misses the gender pay gap reporting deadline?
The Equality and Human Rights Commission (EHRC) enforces compliance with the GPG regulations. Failure to report by the deadline can result in an investigation and, ultimately, an enforcement notice or court order. There are currently no direct financial penalties attached to failure to report, but EHRC enforcement action and the reputational consequences of non-compliance are significant. The EHRC publishes lists of non-compliant employers, which generates substantial press coverage. Many organisations that did not report during the COVID-19 enforcement suspension received media attention that affected employer brand perception.
Does a gender pay gap mean an employer is paying women less than men for the same job?
Not necessarily. The gender pay gap measures the difference in average pay between all male and all female employees — it is primarily driven by representation patterns (more women in lower-paid roles, fewer women in senior roles) rather than direct pay discrimination for equivalent work. Equal pay law — the Equality Act 2010's equal pay provisions — covers the latter: paying women less than men for equivalent work. Both are serious but they are different problems. An organisation can have a significant gender pay gap driven by occupational segregation while paying men and women in equivalent roles identically, and conversely could have relatively equal representation but systematic pay discrimination within roles.
Are self-employed contractors included in GPG calculations?
Genuinely self-employed contractors — those who are in business on their own account, bear financial risk, and are not personally required to perform the work — are not included in the GPG headcount or calculations. Workers under a personal service contract who are not running a business for multiple clients may be included as "workers" for GPG purposes, even if they are nominally self-employed for tax purposes. The IR35 framework for off-payroll workers adds complexity here: workers subject to IR35 are employed for tax purposes, but the GPG regulations use a different legal test. Legal advice is recommended for organisations with significant contractor populations.
How should employers handle employees who are non-binary or decline to disclose their gender?
The GPG regulations as currently drafted require categorisation into male and female groups only. Employees who are non-binary, intersex, or who decline to disclose their gender cannot currently be included in the mandated statistics — they are typically excluded from the calculation, which should be noted in the supporting narrative. The government and EHRC have acknowledged this gap in the regulations and guidance has evolved. Employers should check current Gov.uk and EHRC guidance for the most recent position, document their approach to handling non-binary employees consistently, and note any exclusions in their published narrative.
Gender pay gap reporting is most valuable when it drives genuine action rather than annual compliance paperwork. The organisations with improving year-on-year figures are those that have integrated pay equity analysis into their compensation management cycle, not those that complete the six mandatory metrics and move on. Treegarden's pay equity and compensation analytics provide the infrastructure for ongoing monitoring — tracking the leading indicators of GPG movement (promotion rates, offer distribution, bonus participation) rather than discovering year-on-year change only at reporting time. Request a demo to see how the platform supports your GPG compliance and equity programme.