A £650 annual pay gap sits at the centre of a quiet retention problem spreading across UK workplaces. That figure, drawn from research by HR software specialist Iris Software Group covering 500 UK employees with two to five years of experience and 511 senior HR leaders, represents the average difference between what a seasoned junior earns and what a brand-new hire in the same team is offered. On a payslip it barely registers. In the mind of the person who spent months training that new hire, it registers rather clearly.

The research arrives as the Low Pay Commission continues to advise government on statutory floor increases. Each April uplift to the National Minimum Wage and National Living Wage, set under the National Minimum Wage Act 1998, has pushed entry-level rates upward. For employers that did not match those rises across the whole junior pay ladder, the result is structural compression: the distance between a new starter's offer and a two-year colleague's salary has collapsed, sometimes to nothing at all.

What the numbers actually say

The Iris data, reported by Personnel Today, describes a problem that compounds at each stage. Read the figures in sequence rather than in isolation.

• 71% of young professionals said they struggled to find the motivation to train new hires who earned nearly the same salary as they did.
• 69% of those who discovered what colleagues earned felt undervalued, frustrated, or disappointed.
• A third of affected employees asked their current employer for a pay rise as a direct result of that discovery.
• 16% had already accepted another job offer entirely by the time they were surveyed.

Stephanie Coward, managing director for human capital management at Iris Software Group, framed the pattern in terms that HR teams will recognise: it is not surprising to see frustration building when young professionals are taking on harder work, more responsibility, and helping train the next intake, but see almost no difference in their pay.

The Chartered Institute of Personnel and Development (CIPD), whose annual Reward Management Survey tracks pay practice across around 160,000 member organisations in the UK, has separately highlighted pay equity and transparency as rising concerns among reward professionals. The CIPD's work underscores a structural point the Iris data makes viscerally: organisations that cannot explain the link between experience and pay will struggle to retain the people who hold institutional knowledge.

For employees: what pay compression means for you

If you have two to five years in a role and a newer colleague joined on something close to your current salary, the frustration is legitimate and well-documented. This is a structural pattern that follows from wage-floor policy and employer inertia, not a personal judgement on your performance. The employer hired at today's market rate. Your salary reflects the market rate from one or two years ago, plus whatever uplift the annual pay review delivered, if any.

Before you draft a resignation letter or send a message to a recruiter, a few practical steps are worth taking in sequence.

1. Separate the feeling from the case

The frustration has a legitimate basis. It is not, on its own, a negotiating position. Write down concretely what has changed in your role since you started: new systems you own, people you onboard, projects you lead independently, responsibilities you were not hired to carry. That list is your argument. The £650 gap is the reason you are having the conversation; the expanded scope is the reason it should resolve in your favour. ACAS (the Advisory, Conciliation and Arbitration Service) guidance on pay disputes notes that employees benefit from framing pay requests around demonstrable changes in responsibility rather than comparisons with colleagues alone.

2. Benchmark before you ask

A third of the surveyed employees asked for a pay rise based on what they discovered about colleagues' salaries. The employees who tend to succeed in those conversations bring a market figure, not a grievance. The ONS Annual Survey of Hours and Earnings (ASHE) publishes detailed occupation-level pay data by region each autumn, and it is publicly available. Pair that with verified salary data from wherewework to build a range that reflects your role, city, and sector. Walking in with a range rather than a single number gives the conversation room to move.

3. Decide what a refusal means before the meeting

16% of affected employees had already accepted another offer by the time Iris surveyed them. That outcome is a decision made in advance, not a threat deployed in the room. Before you sit down with your manager, know whether a flat refusal ends the conversation for you or opens a serious search. Employers familiar with retention risk can generally read which situation they are in.

For HR leaders: the visibility gap is the real problem

The HR-side findings from the Iris survey are, in several respects, the harder numbers to sit with. 84% of HR leaders said they were concerned about losing valuable staff over pay compression. Yet only one in five organisations planned targeted salary adjustments to address it. And nearly half of HR leaders expected salary bands to narrow further over the next two years. That combination, high concern and limited planned action, is the structural stall.

The technical explanation is instructive rather than exculpatory: about a quarter of HR leaders said their current systems could not compare pay changes with employee skills and responsibilities. When a payroll platform records what people earn but nothing about what they now do, reward teams are left reacting to resignation letters rather than identifying flight risk in advance. The Equality Act 2010 already requires employers to be able to justify pay differentials if challenged under its pay transparency provisions (sections 77-79), which is additional reason to ensure internal pay data is structurally coherent rather than retrospectively assembled.

Coward's recommendation points directly at the visibility problem: better visibility gives businesses the chance to intervene earlier, whether that means targeted pay adjustments, clearer progression, or simply having a more informed conversation with employees about what their experience is worth.

The Information and Consultation of Employees Regulations 2004 (the ICE Regulations) also give employees in organisations with 50 or more staff the right to request information and consultation arrangements on issues including pay policy. For HR functions that have not mapped their compression risk, a formal ICE request is one possible mechanism through which the issue surfaces publicly rather than privately. Getting ahead of that is straightforwardly better for all parties.

Where to look first

Three starting points for HR and reward teams assessing their own compression exposure in the current financial year:

• Map the two-to-five-year cohort against new starters in the same job family. If the gap is under £1,000 and the responsibility differential is material, that group represents a flight-risk population rather than a payroll rounding issue. The CIPD's Reward Management Survey provides sector-level benchmarks that can help calibrate whether your bands are an outlier or aligned with the market.
• Audit who is training whom. The Iris finding on training motivation is a leading indicator, not a soft metric. If the person running your induction programme feels underpaid relative to the intake they are onboarding, both engagement and onboarding quality deteriorate before anyone has formally resigned.
• Give line managers a defensible script. About a quarter of HR functions cannot benchmark pay against responsibility within their own systems. Until that capability exists, line managers need a clear, factually grounded way to address the question when it arrives from a direct report. It will arrive.

Why 2026 is a sharper moment than previous years

Pay compression is not a new phenomenon. What has shifted materially is the pace at which entry-level floors have moved, driven in part by successive April increases to the National Minimum Wage and National Living Wage under the National Minimum Wage Act 1998, and the speed with which employees now discover what colleagues and competitors pay. Pay transparency, driven partly by industry norms and partly by the salary-sharing behaviour of younger workers, surfaces problems that previously stayed invisible for years.

The Resolution Foundation has documented how real-terms wage growth for mid-experience workers has lagged behind entry-level growth through multiple economic cycles. The Iris data puts a specific number on that lag for the two-to-five-year cohort: £650 a year, on average, separating someone who trains the new intake from the person they are training. When 69% of young professionals who found out what others earned felt undervalued, that transparency is doing what transparency does: it makes a structural problem legible to the person living inside it.

For employees, the practical response is unglamorous. Document your scope, benchmark your role using ASHE and verified peer data, and decide your position before the conversation rather than during it. For HR and reward leaders, the arithmetic is less comfortable: if nearly half of HR leaders expect bands to keep narrowing and only one in five are planning targeted adjustments, the underlying retention risk is not diminishing. The next survey of this kind is unlikely to read better unless the visibility gap closes and the action rate rises to match the stated concern.