When Oxford Economics modelled what it costs a UK business to replace a single employee, the answer was £30,614. Only £5,433 of that was the visible part: advertising, agency fees, interviewing and admin. The other £25,181 was lost output while the new starter got up to speed, which took an average of 28 weeks in firms with more than 250 staff. Now set that against the Job Accommodation Network’s finding that most workplace adjustments cost nothing at all. The cost of neurodivergent staff turnover is one of the most lopsided sums in people management, and it rarely appears in a budget paper.
The cost of neurodivergent staff turnover starts long before the exit interview
Most organisations track the cost of hiring. Far fewer track the cost of leaving. The CIPD’s 2024 Resourcing and Talent Planning report puts the median cost per hire at £1,500 for most employees and £2,000 for senior managers and directors. Those are the numbers that tend to reach finance, and they make turnover look cheap. They are a fraction of the real figure, because the expensive part of losing someone is everything that happens around the vacancy: the months of reduced output before they go, the colleagues who absorb their work, the knowledge that walks out of the door, and the half year it takes a replacement to perform at full speed.
The Oxford Economics study is from 2014, so treat £30,614 as a floor rather than a current price. Salaries have risen since, and so has the cost of the time spent covering gaps. If your organisation loses five capable people a year who could have stayed with better support, that model puts the bill above £150,000 before anyone has looked at morale or client relationships.
Why neurodivergent employees are at particular risk of leaving
The CIPD’s 2024 neuroinclusion research, based on YouGov surveys of over 1,000 employees and over 1,000 senior decision-makers, shows where the pressure builds. Almost a third (31%) of neurodivergent respondents had not told their line manager or HR about their neurodivergence, most often because they saw it as private, feared stereotyping or worried about the impact on their career. A third said their work experience related to their neurodivergence had harmed their mental wellbeing. Neurodivergent employees were more likely than neurotypical colleagues to say they often felt exhausted (45% against 30%) and lonely at work (23% against 17%).
The full report adds the figure a retention strategy should start with. Nearly one in five (19%) neurodivergent respondents said their experience at work had made them less likely to stay with their employer. Among those who had experienced harassment or discrimination, that rose to 36%. Meanwhile only 39% of employers said they ensured clear access to reasonable adjustments, and 39% had taken no action at all aimed at line managers. In other words, the people most likely to leave are often the people your systems cannot see, managed by people who have not been equipped to help.
What retention actually costs
The other side of the ledger is surprisingly small. The US Job Accommodation Network follows up with employers about the adjustments they make and what they cost. In its latest analysis, covering 2019 to 2024, 61% of employers who reported costs said the adjustment cost nothing. Where there was a one-off cost, the median was $300. Only a small minority reported an ongoing annual cost. And 85% of employers said making the adjustment had improved employee retention, the most commonly reported benefit.
For neurodivergent employees, the most useful adjustments are often about how work is organised rather than what is bought: written follow-ups after meetings, clearer priorities, a predictable schedule, a quieter place to concentrate, flexibility over start times, or a manager who checks in on a regular rhythm. None of that requires a capital budget. It requires managers who know what to offer and feel confident having the conversation.
There is a wider wellbeing return too. Deloitte estimated in 2024 that poor mental health costs UK employers £51 billion a year, with presenteeism (people at work but unable to perform at their best) the largest share at around £24 billion. Its review of the evidence found employers get back nearly £4.70 for every £1 invested in supporting mental health. Given how many neurodivergent employees link their work experience to poorer wellbeing, the overlap is hard to ignore.
Building the business case your finance director will accept
The strongest business cases do not lead with values. They lead with your own numbers. Start by working out your voluntary turnover in the last twelve months and attaching a realistic cost to each leaver, using the Oxford Economics split as a template: direct hiring cost plus months of lost output. Then look at where the leavers came from. Are there teams with unusually high attrition, long-term absence or repeated performance processes that ended in departure? Exit data and grievance themes often point to the same few managers.
Next, compare that figure with what you currently spend on preventing it. Many organisations will find they spend tens of thousands replacing people and almost nothing equipping managers to keep them. That gap is the case. You do not need to prove that every leaver was neurodivergent. With nearly a third of neurodivergent employees choosing not to disclose, you will never have complete data, and the practices that help them (clear communication, flexible working, structured one-to-ones) tend to help everyone else as well.
Finally, frame the investment as performance management in its proper sense. When a neurodivergent analyst stays and does well, you keep a skill set, avoid a recruitment cycle and hold on to six months of output you would otherwise have lost.
Turning the numbers into a plan for 2027
Budget season is the moment to move this from good intention to line item. Before your 2027 plans are locked, pull your turnover and absence data together, estimate the cost of last year’s avoidable exits and identify the two or three parts of the business where the problem is concentrated. Check how long adjustment requests take to resolve, because delay is one of the quietest drivers of resignation. Then ask what your line managers have actually been trained to do, rather than what your policy says they should do.
From there, the most cost-effective approach is usually a year-long programme rather than a scattering of one-off sessions: a baseline at the start, manager capability built in stages, policy and adjustments processes tightened, individual support for people who need it, and the same measures checked at the end so you can show the return.
That is what an Enna annual partnership is designed to do. We have worked with more than 750 employers in 33 countries, and we can help you build the cost case and the plan behind it. Book a discovery call to map your 2027 priorities, or start by taking our free Neuroinclusion Maturity Assessment to see where you stand today
Frequently asked questions about neurodivergent staff turnover
How much does it cost to replace an employee in the UK?
Oxford Economics put the average at £30,614 per employee, and most of that is lost output while a new starter gets up to speed rather than recruitment fees. For senior or specialist roles the figure is usually higher, because it takes longer to find the right person and longer for them to reach full productivity.
Why do neurodivergent employees leave their jobs?
It is rarely the work itself. People tend to leave when adjustments are delayed or forgotten, when a manager doesn’t know how to respond to a disclosure, or when performance conversations happen without anyone asking whether a support need has been missed. Most of that sits with line managers, which is why neurodiversity training for managers usually has the biggest effect on retention.
Are reasonable adjustments expensive?
Most are not. The Job Accommodation Network found that most workplace adjustments cost nothing at all, and in the UK Access to Work can help fund some of those that do. Our reasonable adjustments workshop helps managers put the right ones in place quickly and review whether they are working.
How can we tell whether neuroinclusion is improving retention?
Start with a baseline. Track leavers who had disclosed or asked for adjustments, how long adjustments take to put in place and the themes in exit interviews, then compare year on year. The free Neuroinclusion Maturity Assessment gives you a starting point and shows where to focus first, and our neuroinclusion audits go deeper if you need evidence for a board or finance team.
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