Capability or conduct? Why UK employers confuse the two and what it costs when a dismissal falls apart
The operations manager had been in the role for eight months when the managing director decided he had run out of patience. Deadlines kept slipping, two clients had complained in the same fortnight, and the man clearly was not gripping the job. So the director did what felt responsible and started a formal process. He called it a disciplinary action, held a meeting, and issued a written warning for poor performance.
Three weeks later, his HR adviser read the file and asked one question. Was this person refusing to do the job, or struggling to do it? The answer changes everything, and the warning already on file had been built on the wrong one.
This is one of the most common procedural errors we see, and it rarely announces itself. The director was not careless. He was doing what most people do when someone is underperforming, which is to reach for the process that feels decisive. The difficulty is that the law treats poor performance and misconduct as two separate things, with two separate routes, and getting the route wrong at the start is expensive to unpick later.
Can't do the job, or won't do the job
The distinction underneath all of this is simpler than the language around it suggests. Capability is about ability. The employee cannot meet the standard, whether due to a skill gap, a lack of training, or a health issue. Conduct is about behaviour and choice. The person could meet the standard but is not doing so, through carelessness or outright refusal.
The shorthand that holds up under pressure is "can't" versus "won't". Someone who is trying and failing is a capability matter. Someone who is able and declining is a conduct matter. It sounds obvious written down. It is much harder to see clearly when you are frustrated, the client is unhappy, and you simply want the situation dealt with.
The reason it matters is that each route demands a different response from you as the employer. A conduct issue can move to a disciplinary procedure, with an investigation, a hearing, and a sanction where one is warranted. A capability issue asks you to do something slower. You have to set out the standard clearly, provide the support and training needed to reach it, and allow a genuine period to improve before dismissal is even on the table.
Why is the wrong process so easy to start
From the director's perspective, both situations feel identical. Someone is not performing, the business is carrying the cost, and something has to change. The label gets chosen by mood rather than diagnosis.
Two instincts pull in opposite directions here. Some directors reach straight for a disciplinary because it feels like taking control, and a warning feels like progress. Others do the reverse and quietly extend a struggling employee's rope for months, avoiding the difficult conversation entirely, until the frustration finally boils over and they jump to dismissal with no real process behind them. Both start from the same blurred reading of the actual problem.
There is also a quieter trap. Sometimes what looks like conduct is capability wearing a disguise. The employee who has become repeatedly late, or who has gone visibly flat, or whose work has dropped off a cliff, may be dealing with something the business has never thought to ask about. Acas itself notes that a situation that appears to be misconduct can turn out to be a capability or health matter. Start a disciplinary on that footing, and you are not only on the wrong process, but you may also be on the wrong side of the Equality Act before you have realised it.
Where it starts to cost you
Here is the part that catches people out. Both routes are governed by the same standard, the Acas Code of Practice on Disciplinary and Grievance Procedures. That is why directors are often surprised to be told they have done something wrong, because they did follow a process. The trouble is that they followed the process designed for a different problem.
When a capability issue is run as misconduct, the gap shows up quickly. A capability dismissal is only fair if the employee was told plainly where they fell short, given the resources to improve, and allowed a real opportunity to do so. Skip that, treat it as a straight disciplinary, and the eventual dismissal is exposed. A tribunal can find it unfair on procedure alone, even where the underperformance was entirely genuine. A great many capability dismissals fail for exactly that reason. In most of them, the underlying concern was real enough, and what undid the employer was a process that never gave the employee a fair chance to put it right.
Two costs tend to follow. The first is the Acas uplift. Where a tribunal finds you failed to follow the Code unreasonably, it can increase the award by up to 25%. The second is larger and far less predictable. If the underperformance was linked to a health condition or disability and you handled it as a behavioural problem, you may be exposed to a disability discrimination claim on top of the unfair dismissal one. Those awards are uncapped and can include compensation for injury to feelings that an ordinary unfair dismissal claim does not provide.
Even when the problem genuinely is conduct, the disciplinary route has its own well-worn failure points, many of them baked in long before the hearing even starts. And a fair capability route asks more of you than a single improvement chat over coffee. We have set out what managing underperformance properly actually involves in more detail elsewhere, because the gap between an informal nudge and a process that holds up is where most of these cases are won or lost.
The mistake is about to get more expensive
There is a reason to take this more seriously this year than last. Until now, a quiet part of the calculation at the back of many directors' minds has been length of service. An employee with under two years' service generally cannot bring an ordinary unfair dismissal claim, which has softened the risk of getting a process wrong with a newer hire. Discrimination is the exception to that, since those claims need no minimum service, which is part of why the health-linked version of this mistake has always been the dangerous one. That broader cushion, though, is about to thin out considerably.
Under the Employment Rights Act 2025, the qualifying period for ordinary unfair dismissal drops from two years to six months, with effect from 1 January 2027. The statutory cap on compensation comes off at the same time. The timing is the part worth noticing. Anyone hired from around the start of this July will reach six months' service by January 2027 or shortly after, which means this year's new starters are the first group who will gain full unfair dismissal protection within months of joining rather than after two years. The buffer that quietly made a mislabelled process survivable is closing, and the financial ceiling on getting it wrong is being lifted in the same move.
Can you correct it mid-process?
The first question most directors ask, once the penny drops, is whether it can be fixed. The honest answer depends on how far the process has already gone.
If you have only had an early conversation or an initial fact-finding meeting, you usually have room to pause, re-diagnose, and restart on the correct footing. You explain that, having looked at it properly, the right way forward is a capability process rather than a disciplinary one, or the other way round, and you begin again with the proper steps. Handled openly, that is recoverable.
It becomes harder once a formal sanction is on file. A written warning issued for misconduct, when the real issue was capability, does not simply evaporate because you have changed your mind. You may need to address it directly, potentially withdraw it, and explain why. By then, the employee may have taken advice of their own, or lodged a grievance, and the relationship may have taken on a different temperature. A tribunal looks at the whole process rather than the final decision in isolation, so an error near the start can still colour a dismissal that happens months later. A mistake at this stage is not necessarily fatal, but the cost of correcting one rises the longer it goes unnoticed, which is the strongest argument there is for getting the diagnosis right before anything formal begins.
What due diligence looks like before you start
The irony is that avoiding all of this takes very little time at the front end. The work that saves a tribunal is mostly done in the first conversation, before any letter is written.
It starts with a genuine diagnosis instead of a label. Is the person failing because they cannot meet the standard, or because they will not? Have they ever been told clearly, in plain terms, what the standard actually is and where they are falling short of it? Is there anything going on, whether health, personal circumstances, or a change in the role, that might explain a drop from someone who was previously perfectly capable? Has the role itself simply outgrown them, which happens all the time when a strong hands-on worker is promoted into management and then left to sink or swim?
Only once you can answer those questions honestly should you choose the process, because the process should follow the diagnosis and not the other way around. Write down the standard and the specific gap against it. Match the route to what you have actually found. Where it is capability, build in the support and the time to improve. Where it is conduct, investigate properly before you conclude anything at all.
This is the point where having someone outside the situation look at it first earns its keep. A director who is close to the frustration is the least well-placed person in the building to make a cool diagnosis, which is exactly why bringing in structured HR support before a people process begins tends to pay for itself many times over. It is far cheaper to spend an hour getting the diagnosis right than to spend the following six months unpicking a process that was built on the wrong one.
The cost is rarely where you expect it
The operations manager from the opening did eventually leave the business. The director got where he wanted to go. What it cost him was the route he took to get there, because the warning had to be formally unwound and the grievance that followed absorbed months of management time he would far rather have spent on the business.
If that situation looked familiar, here is the question that actually protects you. Before the next people process starts, is anyone stopping to check which process it should be? That single habit, applied at the front of every issue, removes most of the risk described in this article.
If you are weighing up a situation like this right now and you are not certain which process you are actually in, that is the moment to seek a second opinion before the first formal step, rather than after it.
