An SOSR dismissal is the route UK employers take when the reason for dismissal fits none of the usual boxes. A working relationship has broken beyond repair. A major customer refuses to have one of your staff on site. An employee will not accept contract changes the business genuinely needs. SOSR stands for some other substantial reason. It is the fifth potentially fair reason for dismissal in Great Britain, and the least understood of the five. This guide covers what qualifies, the situations tribunals accept, the procedure that keeps the dismissal fair, and the mistake that loses most SOSR cases. That mistake is rarely the reason itself. It is the process around it. 

What an SOSR dismissal is 

The fifth fair reason under section 98 

Section 98 of the Employment Rights Act 1996 lists four potentially fair reasons for dismissal. They are capability or qualifications, conduct, redundancy, and statutory illegality, where the person can no longer legally do the job. 

Section 98(1)(b) then adds a fifth. An employer may dismiss for "some other substantial reason of a kind such as to justify the dismissal" of an employee in that position. GOV.UK's guidance for employers names the same fifth category and confirms a valid reason can sit outside the four named ones. 

Parliament knew it could not list every legitimate reason a business might one day have. So it left a fifth door open. SOSR is that door. It exists for the genuine situations the first four categories miss, and for nothing else. 

What "substantial" means in practice 

The Act does not define substantial. Tribunals read it broadly. The reason must be genuine, more than trivial, and capable of justifying the dismissal of someone in that particular role. That is a lower bar than most employers expect. 

Here is the part most owners get wrong. Facing an SOSR decision, they worry about whether the reason is substantial enough. It usually is. Tribunals rarely reject an SOSR case because the reason failed the test. They reject it because the employer treated a qualifying reason as permission to skip a fair process. SOSR is a low bar on the reason and a high bar on the procedure. Every section below builds on that fact. 

Substantial does have limits. Personal dislike is not SOSR. A vague loss of trust with no evidence behind it is not SOSR. Wanting to replace someone with a cheaper hire is not SOSR. The reason must stand up as a business reason on its own feet, documented at the time, not assembled later. 

A quick test before you go further. Write the reason in one plain sentence, dated, before the process starts. If you cannot, you do not yet have a substantial reason. You have a frustration, and frustrations do not survive tribunal scrutiny. 

Where SOSR sits next to conduct, capability, redundancy and illegality 

SOSR is a genuine fifth category, not a dustbin for awkward cases. The label you pick decides the procedure you must run. Conduct needs an investigation, a disciplinary hearing and warnings where they fit. Capability needs standards, support and time to improve. Redundancy needs fair selection and consultation. 

Pick SOSR when the facts genuinely sit outside those routes. Never pick it because the proper route feels slow. A tribunal looks at the substance of the reason, not the name the employer gave it. If the real issue was conduct, the tribunal treats the case as conduct, and judges you against the process you should have run. More on that trap below, because it is the fastest way to lose. 

Common situations that count as some other substantial reason 

Six situations come up again and again in SOSR cases. Each can qualify. Each carries its own test, and its own paperwork. 

Irretrievable breakdown in working relationships 

The most common SOSR route in small businesses, and the most dangerous. Two people cannot work together any more. The atmosphere is poisoning a small team. The owner concludes someone has to go. 

A relationship breakdown can be SOSR. A tribunal will then ask three hard questions. Who caused the breakdown? What did you do to repair it before reaching for dismissal? Is this a conduct or capability problem wearing a friendlier label? If the file shows no mediation, no structured conversation, no team move considered, no genuine repair attempt, expect to lose. Tribunals examine the breakdown route harder than the named reasons, not softer, because they know how often it hides a process the employer wanted to avoid. 

The operational fix is simple. Date-stamp every repair attempt as it happens. An email offering mediation, minutes of a clear-the-air meeting, a note of a redeployment option weighed and declined. That file is the difference between a breakdown and an excuse. 

Refusal to accept a lawful change to contract terms 

Businesses change. Shift patterns, pay structures, duties and locations sometimes have to move with them. Where an employee refuses new terms after proper consultation, and the business reason is sound, dismissal can be SOSR. 

The strength of the case sits in the business reason and the consultation, not in the refusal. You need evidence the change mattered commercially: falling margins, a lost contract, a site consolidation, set out in writing before the process started. You also need a record showing you explained the change, listened to objections, and considered alternatives. Be aware the Employment Rights Act 2025 tightens the rules around dismissal and re-engagement on a phased timetable, with the restrictions expected to take effect from October 2026. If your plan involves dismissing staff to re-hire them on new terms, take advice before you start, not after. 

Third-party pressure to remove an employee 

A key customer bans your engineer from their site. A regulator or insurer will not cover a named individual. Pressure from a third party can be SOSR, even where the employee did nothing wrong. 

The tribunal expects three things from you. Show the pressure was real and sustained, in writing, not a remembered phone call. Show you pushed back where you reasonably could. Show you looked hard for alternatives, redeployment above all. The tribunal also weighs the injustice to the employee, precisely because they may be blameless. A dismissal that shrugs and says the customer insisted, with nothing else on file, will not survive scrutiny. 

Reputational risk and external events 

An employee is charged with a serious offence outside work. The role involves trust, money or vulnerable people. Continued employment could damage the business's standing. Reputational risk can qualify as SOSR where there is a clear connection between the event and the role. 

The connection is the test. A warehouse operative and a finance director carry different reputational weight for the same event outside work. Investigate what happened rather than relying on headlines, assess the concrete risk to the business, and record that assessment before deciding anything. A charge is not a conviction, and a panicked same-week dismissal reads as exactly that in a tribunal bundle. 

Expiry of a genuine fixed-term contract 

In law, letting a fixed-term contract expire without renewal counts as a dismissal, so it needs a fair reason like any other. The end of a genuine temporary need can be SOSR. GOV.UK uses this example: an employee taken on to cover maternity leave, told clearly at the start that the role was temporary, fairly dismissed when the cover ends. 

The word genuine carries the weight. State the temporary purpose in the contract itself. Rolling fixed-term renewals used to avoid permanent status attract tribunal scepticism, and if the role carried on with someone else in it, expect that question at the hearing. 

A business reorganisation that is not redundancy 

Some reorganisations reshape jobs without reducing headcount, so the statutory definition of redundancy is never met. The same work continues, structured differently. Dismissing an employee who cannot or will not move to the reshaped role can be SOSR, provided the reorganisation had sound business reasons and you consulted properly. 

Owners often mislabel these cases as redundancy, then fail redundancy tests they never needed to sit, starting with the absence of a true reduction in work. Get the category right before you start, because the category decides the process, the paperwork and the payments. Where the reshaped role is broadly similar on pay and standing, offer it in writing and record the employee's response. That one document often decides the case. 

Why a substantial reason is not enough on its own 

The section 98(4) reasonableness test 

Establishing SOSR clears stage one. Stage two decides the case. Under section 98(4), the tribunal asks whether you acted reasonably in treating that reason as sufficient to dismiss, taking account of your size and resources, equity, and the substantial merits of the case. 

This is where SOSR dismissals die. The reason can be watertight and the dismissal still unfair, because nobody was consulted, no alternative was weighed, and nothing was written down. Our guide to when dismissing someone becomes an unfair dismissal walks through this two-stage structure across all five fair reasons. For SOSR, stage two is nearly the whole game. 

The size-and-resources wording matters for SMEs. A five-person firm is not judged against a corporate HR department. It is still judged. Small means the process can be simpler. It never means the process can be skipped. 

The band of reasonable responses 

The tribunal does not ask what it would have done in your shoes. It asks whether dismissal sat within the range of responses a reasonable employer could take on those facts. That protects employers who make defensible judgement calls between fair options. 

It does not protect employers who cannot show how the judgement was made. A decision with no consultation, no alternatives considered and no record sits outside the band, whatever the underlying reason. The band test rewards visible reasoning, and visible means written. 

A fair procedure and the ACAS Code 

The ACAS Code of Practice on disciplinary and grievance procedures formally covers discipline and grievance cases, and some SOSR dismissals sit outside its strict scope. Do not let that comfort you. Tribunals expect the same shape of fairness in every dismissal: a genuine investigation, a meeting, a chance to respond, an appeal. 

So follow the Code's steps in every SOSR case. Where it strictly applies, you are covered. Where it does not, you have still built the fairness section 98(4) demands. There is no version of an SOSR dismissal that is safer for having less process. 

The procedure to follow before an SOSR dismissal 

An SOSR dismissal is a with-notice dismissal built on evidence. It never justifies dismissing on the spot. Ending employment without notice belongs to gross misconduct cases, and even then only after a proper process, as our guide to being summarily dismissed explains. The employee keeps their notice entitlement, worked or paid in lieu; our PILON payment guide covers that mechanics. For the SOSR decision itself, four steps do the work. 

1. Investigate and evidence the reason 

Gather the facts before forming the view. For a breakdown, that means speaking to the people involved and recording what each said. For a contract change, it means the business case in writing before consultation opens. For third-party pressure, it means the customer's demand in an email. Every SOSR case rests on proving the reason was real, current and pressing, and proof means documents. 

2. Consult the employee and consider alternatives 

Put the problem to the employee before any decision is made. Listen to the answer. Then weigh the alternatives properly: mediation, redeployment, adjusted terms, a different site, more time. You are not required to adopt an alternative. You are required to show you considered it seriously and can say why it failed. Consultation that happens after the decision is not consultation, and tribunals can read that sequence straight off the dates on the paperwork. 

3. Hold a hearing and offer an appeal 

Hold a formal meeting before deciding. Set out the reason, share the evidence, and let the employee respond to it. Allow a companion even where the strict legal right does not bite; it costs nothing and reads as fairness. Confirm the outcome in writing with the reason spelled out plainly. Then offer an appeal, heard by someone who was not part of the original decision wherever the size of the business allows. 

4. Keep contemporaneous written records 

A note written on the day something happened beats a statement written for the hearing. This is the cheapest protection a small employer can buy, and it costs minutes. Date-stamped file notes, minutes of every meeting, emails weighing the alternatives. These records prove the process was real. Records assembled after the fact do the opposite. They suggest the process was theatre, and tribunals read dates with care. 

Where employers lose SOSR cases at tribunal 

The cost of getting this wrong runs past any award. Management time, legal fees and months of distraction mount long before a hearing, as our review of employment tribunal costs sets out. Five failures account for most SOSR losses. 

Mislabelling a conduct or capability issue as SOSR 

The fastest route from defensible to unfair. An employer with a performance problem dreads the slow grind of a capability procedure, so the situation gets rebadged as a relationship breakdown. The tribunal looks through the label at the facts, finds a capability case with no standards set and no chance to improve, and the dismissal fails. If the facts fit a named reason, run that procedure. SOSR is for reasons the categories miss, never for processes the employer wants to miss. 

Thin or back-dated paperwork 

An entirely justified dismissal loses when the paper trail is thin or built after the event. The decision was sound; the evidence of how it was reached does not exist. Under section 98(4) the tribunal judges your process, and an undocumented process cannot be defended even where it genuinely happened. Write things down on the day. Repetition intended: it decides cases. 

No genuine attempt to repair a relationship breakdown 

Tribunals treat repair attempts as the entry fee for the breakdown route. Mediation offered, a team move explored, a clear-the-air meeting held and minuted. Where the file shows the employer simply waited for the relationship to get bad enough to act on, the breakdown starts to look engineered, and the dismissal unfair. 

Skipping consultation on a contract change 

The business reason for new terms can be impeccable. Impose the change without genuine consultation and the dismissal of a refusing employee still fails. Consultation is your evidence that the change was necessary and the refusal unreasonable. Without it you hold an assertion, not a case. 

Treating the appeal as a rubber stamp 

An appeal heard in ten minutes by the person who made the original decision is worse than no appeal on paper, because it shows the outcome was fixed. A genuine appeal, heard fresh, sometimes reverses a bad call before a claimant ever contacts ACAS. That is the appeal doing exactly the job the tribunal expects it to do. 

SOSR and the law changing in January 2027 

The qualifying period is shrinking 

Today, an employee usually needs two years' service to bring an ordinary unfair dismissal claim, while claims such as discrimination and the automatically unfair reasons need no qualifying period at all. These figures, and the changes below, apply in England, Scotland and Wales. In Northern Ireland the qualifying period is usually one year and the Employment Rights Act 2025 changes do not apply. GOV.UK confirms the two-year rule and the automatically unfair exception, and confirms the change coming: from 1 January 2027, most employees will be able to claim unfair dismissal after six months. The change flows from the Employment Rights Act 2025. 

Today a claimant must usually notify ACAS within three months minus one day of dismissal. The Employment Rights Act 2025 is expected to stretch that limit to six months for most claims from October 2026. The exposure window is what widens: a far larger share of your workforce will hold full unfair dismissal rights. 

Why your process matters more, not less 

Under today's rules, many SOSR situations involving newer staff carry limited ordinary unfair dismissal risk. From January 2027 that quietly ends. An employee with seven months' service will hold the same claim rights as a ten-year veteran, and SOSR decisions about recent hires will face full section 98(4) scrutiny. 

The employers who cope will be the ones whose process is already habit before the law lands: consult, weigh alternatives, hold the hearing, write it down the same day. Build the habit now, on the two-year rule, and January 2027 changes nothing about how you operate. If there is nobody in the business to build that habit, outsourced HR support is the practical fix for an SME. The law is moving the goalposts toward process. SOSR cases were always won there anyway. 

Facing a dismissal that does not fit the usual boxes? 

SOSR decisions are judgement calls with a tribunal watching. The reason is usually the easy part. Whether your evidence, consultation and paperwork would survive section 98(4) is the hard part, and it is close to impossible to see your own gaps from inside the situation. The HR Doctor works directly with SME owners and managers on exactly these decisions, before they become claims. Book a free 30-minute discovery call: https://assist.hrdr.co.uk/appointment