Do I have to give a written warning first?

Alan Creevy, Founder · 10th November 2026

No sentence in UK employment law tells you how many warnings to give before you dismiss someone. Not one, not three, not any number at all. The rule most employers believe in is a convention that grew up around the law rather than a part of it, and once you can see the difference you can also see which bits of it you are free to skip and which bits you are not.

What the law actually asks of you

Unfair dismissal turns on two questions, both in section 98 of the Employment Rights Act 1996. First, was your reason one of the permitted ones: conduct, capability or qualifications, redundancy, a legal restriction that makes the job impossible, or some other substantial reason. Second, under section 98(4), did you act reasonably in treating that reason as sufficient to dismiss.

Warnings appear nowhere in that test. Section 98(4) does not list steps. It asks whether you acted reasonably “in the circumstances”, and it says those circumstances include “the size and administrative resources of the employer’s undertaking”. That phrase sits in the Act itself, and it is the most useful thing in it for a business of nine people. You are not measured against what a company with an HR department would have done.

The government’s own guidance puts the same point more bluntly. On dismissals for conduct or performance it says there is “no specific process you must go through by law”, as long as you do it fairly.

So where did three warnings come from

From the Acas Code of Practice on disciplinary and grievance procedures and from a generation of staff handbooks that copied it without reading it closely.

Paragraph 19 of the Code says that where misconduct is confirmed or performance is unsatisfactory, “it is usual to give the employee a written warning”, and that a further offence or a failure to improve “would normally result in a final written warning”. Usual, and normally. Paragraph 20 then says that where a first instance is serious enough, “it may be appropriate to move directly to a final written warning”. The Code describes a default and then describes how to depart from it.

The Code matters, but not in the way people assume. Failing to follow it does not by itself make you liable for anything. What it does is allow a tribunal to adjust an award by up to 25% where a party failed to comply with the Code and that failure was unreasonable, under section 207A of the Trade Union and Labour Relations (Consolidation) Act 1992. In an unfair dismissal claim that adjustment is applied to the compensatory award, not to everything you might end up paying, under section 124A of the Employment Rights Act 1996. Note the word unreasonable. Departing from the Code for a reason you can explain is not the same as ignoring it.

The three cases where you can skip a warning

Gross misconduct. Paragraph 23 of the Code says such cases “may call for dismissal without notice for a first offence”, while insisting that “a fair disciplinary process should always be followed, before dismissing for gross misconduct”. The examples in paragraph 24 include theft or fraud, physical violence, gross negligence and serious insubordination. No warning is needed here. The investigation, the meeting and the chance to respond still are.

Serious, but not gross. Here you compress rather than skip. The government’s guidance says you can issue a single warning that is both the first and the final one where the misconduct or underperformance is serious enough, and paragraph 20 of the Code says the same. This is the branch most employers miss, and it is very often the right one.

Poor performance where support has already been tried. Acas expects you to help someone improve before any formal procedure starts, through training, coaching or a plan to improve. It also says dismissal should be a last resort. Paragraph 20 of the Code covers unsatisfactory performance as well as misconduct, so if you have genuinely given that support over a period of months, the first formal step can reasonably be a final written warning rather than a first one. What you cannot do is produce the support retrospectively.

The real risk is not the missing warning

Here is what actually goes wrong at tribunal, and it is worth understanding because it changes what you do next.

A written warning is not a magic document. It is a mechanism for doing three things: telling someone clearly what the problem is, telling them what has to change and by when, and telling them their job is at risk if it does not. Paragraph 21 of the Code sets out that content. Dismissals without warnings rarely fail just because the paperwork was missing. They fail because the employee can say, truthfully, that nobody ever told them the standard, or that they never understood their job was on the line, or that they were not asked for their side before the decision was taken.

So the question to put to yourself is not “have I given a warning”. It is “can this person honestly say they did not see this coming, and that nobody asked them for their account”. If the answer to that is yes, three warnings would not have saved you either, because you would have issued all three without ever doing the thing they exist to do.

Your own handbook can take the choice away

This is the trap that catches small employers most often. The law gives you latitude. Your own written procedure may quietly have given it back.

If your handbook or your contracts say you will give a first written warning, then a final one, then dismiss, you have told your staff that is what happens. Departing from it is a departure from your own stated process, and a tribunal will want to know why. So read what you have actually promised before you decide anything. If it is tighter than the law requires, either follow it or be able to explain, in writing, why this case was different.

What to do this week

Write down three things before you act: the standard you expected, what the person actually did, and every occasion on which you have already raised it, with dates. That last list usually decides which branch you are on.

If it is gross misconduct, investigate, invite them to a meeting in writing, hear them, then decide. If it is conduct or performance falling short of that, decide honestly whether this is a first warning case, a final warning case or a dismissal case. Record the reason for your choice. Either way, leave sensible gaps between the steps. Five working days from the invitation to the meeting, three from the meeting to the written outcome, and five for an appeal are reasonable starting points, and the free timetable will put real dates against them. Acas says you should offer an appeal, so offer one.

One piece of timing is worth knowing. Today an employee needs two years of continuous service to bring an ordinary unfair dismissal claim. From 1st January 2027 that drops to six months, fixed by regulations made this year. Decisions you take loosely about people in their first couple of years, including anyone still on probation, are about to become challengeable in a way they are not today, and we have written separately about what the move to six months means in practice. The habit worth building now is the one that will serve you then: say what the standard is, say it in writing, and let the person answer before you decide.

Tarn.hr provides HR guidance based on UK employment law and Acas codes of practice. It does not constitute legal advice and should not be relied upon as such. Employment law is complex and turns on the facts of each case. For any situation involving significant legal risk, potential tribunal claims, or matters of particular sensitivity, you should seek advice from a qualified employment solicitor. Tarn.hr is not responsible for any decisions made on the basis of its guidance.