Rethinking Probation: Managing Underperformance and Early Intervention Under the Six-Month Rule

Under the current two-year qualifying period, many employers manage underperformance during probation informally — a quiet conversation, no written record, and if things don't improve, the employee leaves before any legal rights attach. From 1 January 2027, that approach carries real financial risk. The Employment Rights Act 2025 reduces the unfair dismissal qualifying period to six months, meaning an employee dismissed after Day 182 without documented evidence of a fair process can bring a claim with uncapped compensation. ACAS guidance requires employers to take steps to help an employee improve before starting a formal procedure. Legal commentary from DLA Piper and Bird & Bird confirms that what was once quick and informal now requires formal warnings, a performance improvement plan, and a carefully documented fair process.

ProbationWatch builds structured review records at every stage of probation — so when performance issues arise, your documentation trail is already in place. See how it works →

How Early Should Performance Issues Be Addressed During Probation?

Immediately. Not at the mid-point. Not in the final month. The moment a concern is identifiable, it should be raised with the employee and recorded.

This is not about being punitive. It is about fairness — to the employee and to the employer. An employee who is told at Day 150 that they have been underperforming since Day 30 has a legitimate grievance: they were not given a fair chance to improve. A tribunal will see it the same way.

DLA Piper's guidance on the impact of the unfair dismissal changes is explicit: employers must tackle performance or conduct issues early and follow the ACAS Code of Practice. Bird & Bird notes that the shift from a two-year to a six-month qualifying period means the old approach of handling things informally is no longer sustainable — structured, documented intervention is expected from early in the employment.

The practical rule: if you would mention a concern to a colleague over coffee, it should already be in the employee's probation file.

What Should You Do If an Employee Is Underperforming on Probation?

The process is not complicated, but it must be followed consistently and documented at every step.

Step 1: Identify the specific issue

Avoid generalities. "Not performing well" is not actionable. "Has missed three out of five weekly reporting deadlines in the last month" is. Before raising a concern, define exactly what the employee is not doing, what they should be doing, and how you know the gap exists.

Reference the written objectives set at the start of probation. If no objectives were set — that is itself the first problem to fix. Without a documented standard, you cannot fairly assess someone against it.

Step 2: Raise the concern promptly and in writing

Have a direct conversation with the employee. Explain the specific concern, give examples, and ask for their perspective. There may be circumstances you are not aware of — a training gap, an unclear brief, a personal difficulty.

After the conversation, produce a written record: what was discussed, what examples were given, what the employee said, and what was agreed. This record does not need to be a formal disciplinary document — at this stage, it is a probation review note. But it must exist.

Step 3: Agree an improvement plan

Set clear, measurable targets for what needs to change, by when. The plan should include the specific behaviours or outputs expected, the support the employer will provide (training, mentoring, clearer instructions, additional resources), a defined review date (typically two to four weeks), and a clear statement of what happens if improvement is not achieved.

This is the step most employers skip — and it is the step tribunals scrutinise most closely. An employer who dismissed without offering support to improve will struggle to demonstrate a fair process.

Step 4: Provide the agreed support

If you committed to training, schedule it. If you offered mentoring, assign a mentor. If you agreed to weekly check-ins, hold them. Document each action taken. An improvement plan that exists on paper but was never implemented is worse than no plan at all — it creates evidence that the employer knew what was needed and failed to deliver it.

Step 5: Review at the agreed date

At the review point, assess progress against the specific targets set in the improvement plan. Record the outcome in writing: has the employee improved, partially improved, or not improved? If improvement has occurred, acknowledge it and set expectations for sustained performance. If it has not, escalate — and ensure the written record reflects the escalation clearly.

Step 6: Escalate or decide

If the employee has not improved after documented feedback, a clear improvement plan, and genuine support, the employer is in a defensible position to make a probation decision. The decision — whether to extend probation, offer a final review period, or dismiss — must be communicated in writing with reference to the documented process.

Can You Dismiss Someone on Probation for Poor Performance?

Yes — but from January 2027, the process matters as much as the reason.

Under the current two-year qualifying period, employers can generally dismiss a probationary employee for performance reasons without needing to demonstrate a formal fair process (subject to discrimination and other automatically unfair dismissal protections). From January 2027, an employee who has completed six months of continuous service can claim ordinary unfair dismissal. The employer must then show both a fair reason and a fair procedure.

Capability — the employee's ability to do the job — is a recognised fair reason for dismissal. But the procedure must demonstrate that the employee knew what was expected, was told they were falling short, was given support and time to improve, and was warned of the consequences if they did not.

Common reasons for dismissal during probation include lack of skills or capability for the role, persistent poor timekeeping, failure to meet defined objectives, and — in more serious cases — gross misconduct. For capability-related dismissals, the ACAS Code of Practice requires a structured process even where the employer considers the issue straightforward.

The practical message for managers: the right to dismiss for poor performance has not changed. What has changed is the standard of process and documentation required to make that dismissal defensible.

What Is the ACAS Process for Underperformance During Probation?

ACAS does not publish a separate process for probation — its guidance on managing performance applies to all employees. The core principle is that employers should take steps to help someone improve before starting a formal disciplinary procedure.

In practice, this means the ACAS-compliant approach to underperformance during probation follows this sequence:

Identify and raise the issue early. Do not wait for a formal review point. If performance concerns are visible, they should be raised with the employee promptly.

Be specific about what needs to change. General dissatisfaction is not a basis for action. ACAS expects employers to explain clearly what the required standard is and how the employee is falling short.

Offer support. Training, mentoring, adjusted workload, clearer direction — whatever is reasonable and relevant to the issue. The employer must be able to show they tried to help the employee succeed.

Allow reasonable time to improve. What counts as reasonable depends on the nature of the role and the issue. For a straightforward skills gap, two to four weeks may be sufficient. For more complex capability concerns, a longer period may be expected — but the six-month statutory deadline means this period cannot be indefinite.

Review and record. Assess whether improvement has occurred, document the assessment, and decide on next steps.

Follow a fair process for any dismissal. If the decision is to dismiss, ACAS expects a formal meeting, the right for the employee to be accompanied, a clear explanation of the reasons, and the right to appeal.

Failure to follow the ACAS Code of Practice can result in tribunal compensation being increased by up to 25%. From January 2027, with the compensation cap removed, that uplift applies to an uncapped base figure — making non-compliance significantly more expensive than it has been historically.

What Is a Performance Improvement Plan During Probation?

A performance improvement plan (PIP) during probation is a written document that sets out specific areas where the employee is not meeting the required standard, measurable targets for improvement, the support the employer will provide, a defined timeline for achieving the targets, and the consequences if improvement is not achieved.

A PIP during probation is typically shorter and more focused than one used for a long-standing employee — weeks rather than months, and targeted at the core requirements of the role rather than a broad development agenda.

When to use a PIP during probation

Not every performance concern requires a formal PIP. For minor issues identified early — say, at the Day 30 check-in — a documented conversation with agreed actions may be sufficient. A PIP is appropriate when concerns are significant and have persisted despite informal feedback, the employee needs a structured framework to understand what is expected and by when, or the employer wants to create a clear, documented record that a fair improvement opportunity was given before a decision is made.

What makes a PIP defensible

A PIP that will withstand tribunal scrutiny has four characteristics. First, it is specific — vague targets like "improve attitude" are not measurable and will not be taken seriously. Second, it is supported — the employer commits to concrete actions, not just expectations. Third, it is time-bound — the employee knows exactly when they will be assessed. Fourth, it is documented — the plan, the review, and the outcome are all in writing and stored securely.

CIPD's 2024 research found that 41% of UK employers regretted at least one hiring decision in the preceding 12 months. In many of those cases, a structured improvement plan during probation could have either resolved the issue or created the documentation needed for a defensible dismissal.

ProbationWatch structures every review around objectives, feedback, support, and decisions — so if a PIP is needed, the foundation is already built. Start your free trial →

Scenarios: What Early Intervention Looks Like in Practice

Abstract guidance is useful. Concrete scenarios are more useful. Here are three situations a line manager might face during probation, and how to handle each.

Scenario 1: The missed deadlines

Your new marketing coordinator has missed three campaign deadlines in six weeks. The work quality is acceptable when delivered, but the timekeeping is creating problems for the rest of the team.

What to do: Raise the concern at the earliest opportunity — do not wait for the scheduled Day 60 review. Have a one-to-one conversation: state the specific deadlines missed, explain the impact, and ask why it is happening. There may be a workload issue, a skills gap in project management, or a misunderstanding about priorities. Agree a plan: specific deadlines for the next four weeks, weekly check-ins on progress, and any support needed (a project management tool, a clearer brief process). Document the conversation and the plan. Review at the agreed date. If deadlines are met, record the improvement. If not, escalate with a formal written warning that probation is at risk.

Scenario 2: The cultural misfit

Your new team member is technically capable but is creating friction — interrupting colleagues in meetings, dismissing feedback, and working in isolation when collaboration is expected.

What to do: This is harder to document but no less important. Define the specific behaviours you have observed — not "doesn't fit in," but "interrupted three colleagues during Tuesday's team meeting" or "did not respond to two requests for input on the shared project brief." Raise the concern directly, referencing the behaviours and the team expectations that were set during onboarding. If expectations around collaboration were not documented at the start, set them now in writing. Agree specific behavioural changes, provide support (coaching, a buddy, structured collaboration opportunities), and review in two to three weeks. Record everything.

Scenario 3: The slow starter

Your new analyst is struggling with the technical aspects of the role — producing work that requires significant correction, taking longer than expected on routine tasks, and asking questions that suggest gaps in foundational knowledge.

What to do: Assess whether this is a capability gap (they lack the skills) or a support gap (they were not given adequate onboarding or training). If it is a skills gap, be honest early — not at Day 150. Set a structured improvement plan: specific skills to develop, training to complete, measurable output targets, and a review date. If the training was inadequate, fix it — and document that you did. If the employee improves, record it. If the gap persists despite genuine support, the documentation trail positions you for a defensible decision.

The Manager's Role: Why Training Matters

The person conducting the probation review, raising the concern, and documenting the outcome is almost always the line manager — not an HR professional. In organisations with fewer than 50 employees, there may be no dedicated HR function at all.

Brightmine's 2025 research found that fewer than half of UK organisations provide line manager training on managing probation. That means the majority of probation processes are being run by people who have not been equipped to do them well.

The consequences are predictable. Managers avoid difficult conversations because they have not been taught how to have them. Concerns go unraised until the final weeks of probation — too late for a fair improvement process. Documentation is patchy or absent because no one explained what to record. Decisions are made on instinct rather than evidence.

From January 2027, those gaps translate directly into legal risk. Training managers to identify performance issues early, raise them constructively, document consistently, and follow a structured review process is not a nice-to-have — it is a compliance investment.

The training does not need to be elaborate. Managers need to understand the six-month statutory deadline and why it matters, how to set clear objectives and assess performance against them, how to have a constructive performance conversation, what to document and when, and when to escalate to HR or seek external advice.

Frequently Asked Questions

How do you manage underperformance during probation?

Identify the specific issue early, raise it with the employee promptly and in writing, agree a clear improvement plan with measurable targets and support, review at the agreed date, and escalate if improvement does not occur. Document every step. The earlier you act, the more defensible your process.

What should you do if an employee is underperforming on probation?

Have a direct conversation, referencing specific examples against the objectives set at the start of probation. Agree an improvement plan with defined targets, support, and a review date. Document the conversation, the plan, and the outcome. If improvement does not occur after genuine support, the documentation trail supports a fair decision.

Can you dismiss someone on probation for poor performance?

Yes. Capability is a fair reason for dismissal. From January 2027, employees with six months' service can claim unfair dismissal, so the employer must demonstrate both a fair reason and a fair procedure — including documented objectives, feedback, support, and the opportunity to improve.

What is the ACAS process for underperformance during probation?

ACAS guidance requires employers to raise concerns early, be specific about what needs to change, offer support, allow reasonable time to improve, and follow a fair process for any dismissal — including a formal meeting, the right to be accompanied, and the right to appeal. Failure to follow the ACAS Code can increase tribunal compensation by up to 25%.

How early should performance issues be addressed during probation?

Immediately. Concerns should be raised as soon as they are identifiable, not deferred to a scheduled review point. An employee told at Day 150 about an issue visible since Day 30 has a legitimate grievance that the employer did not give them a fair chance to improve.

What is a performance improvement plan during probation?

A PIP is a written document setting out specific underperformance areas, measurable improvement targets, employer-provided support, a defined timeline, and the consequences of not improving. During probation, PIPs are typically shorter and more focused than those used for established employees.