Can I Write a Job Description After I've Already Hired Someone? (Yes, and You Should Do It Today)

“I hired Dave six months ago. Great bloke, works hard, but I’m realising we never actually wrote down what his job is. He’s sort of doing a bit of everything, and now I need to hire someone else but I can’t figure out where Dave ends and the new person begins. Can I write a job description now, or have I missed the boat?”

This is one of the most common situations I see with SME owners. You find someone good, you hire them quickly (because let’s face it, good people don’t hang around), and then you figure out the paperwork later.

Here’s the good news: yes, you absolutely can write a job description after someone’s already working for you. In fact, you should do it as soon as possible. And no, it’s not weird, awkward, or a sign that you don’t know what you’re doing - it’s just smart business. It’s about to get more important too, so read to the end on this one.

Why This Happens More Than You’d Think

Let’s be honest about how hiring actually works in small businesses. It’s rarely the textbook process of “write job description, advertise role, interview candidates, hire perfect match.”

More often it goes like this:

• Someone leaves suddenly
• You’re desperate for help
• A mate recommends someone
• They seem decent, so you hire them
• They start doing whatever needs doing
• Six months later you realise nobody actually knows what their official job is

Sound familiar? You’re in good company. About 70% of the SME owners I work with have at least one person whose role has evolved organically without any formal documentation.

The Problem with “Winging It”

Here’s what happens when someone’s been working without a clear job description:

Role creep becomes a nightmare. Dave starts helping with deliveries because you’re short-staffed. Then he’s doing some basic admin. Before you know it, he’s somehow responsible for your entire stock system, but nobody agreed to that and he’s not getting paid for the extra responsibility.

Performance management becomes impossible. How do you have a meaningful conversation about Dave’s performance when neither of you can actually define what he’s supposed to be doing?

Other staff get frustrated. Sarah’s been doing admin for three years, but now Dave’s doing some of it too. Who’s responsible for what? Cue the office politics.

You can’t scale the business. Want to hire another Dave? What exactly is he hiring them to do? You end up with job adverts that read like “general dogsbody wanted” - not exactly attracting top talent.

“But Won’t It Look Like I Don’t Know What I’m Doing?”

This is the worry I hear most often. Business owners think that writing a job description months after hiring someone makes them look disorganised or unprofessional.

Here’s the reality: your employees want clarity. They want to know what’s expected of them, how they’ll be measured, and where their responsibilities begin and end. Far from looking incompetent, taking the time to formalise their role shows you’re a thoughtful leader who cares about doing things properly.

The Legal Bit (This Is the Part That’s Changing)

Under UK employment law, you have to provide written particulars of employment - job title, place of work, hours, pay - on or before day one (that’s been the rule since April 2020). A handful of wider terms (pensions, collective agreements, non-compulsory training, and disciplinary and grievance procedures) technically get up to two months, but build your process as if that window does not exist: the practical standard is everything in their hands on or before day one. If you haven’t done that for Dave, you’re technically in breach right now. Not the end of the world, but not ideal either.

Two things to get in your head:

Why it can’t wait: You need mutual agreement on terms before work begins. And here’s the heads-up: since April 2020 the written particulars have been a day-one right - in their hands on or before day one. A few wider terms (pensions, collective agreements, non-compulsory training, and disciplinary and grievance procedures) technically get up to two months, but treat that window as something you never plan to use: the standard you hold yourself to is the full document before they start. Get into the “contract signed before they start” habit now and you’ll never have to think about it again.

From 1 January 2027, dismissal law gets sharper teeth - for both sides. The qualifying period for unfair dismissal drops from two years to six months, and the compensation cap goes. If you ever need to take disciplinary action against Dave, or worse, you have to be able to show exactly what he was employed to do and how he failed to meet it. “Well, he sort of did a bit of everything” is not evidence. A signed job description is.

And since October 2026, claims can be brought up to six months after dismissal rather than three - so the argument arrives later and stays longer. Sort the paperwork now, while it’s still easy.

More importantly, if you ever need to take disciplinary action or, worst case, dismiss someone, having a clear job description is absolutely crucial. You need to be able to show exactly what they were employed to do and how they failed to meet those requirements.

How to Write a Job Description for Someone Already in Post

This is actually easier than writing one from scratch, because you can see what the person actually does day-to-day. Here’s the process:

Step 1: Have an honest conversation. Sit down with your employee and explain what you’re doing. Something like:

“Dave, I realise we’ve never properly documented what your role involves, and I want to put that right. It’s not because you’re doing anything wrong - quite the opposite. I want to make sure we both have a clear understanding of your responsibilities and that you’re properly recognised for everything you do.”

Step 2: Map out their current reality. Ask them to list everything they actually do. Not what they think they should be doing, but what they actually spend their time on. You might be surprised.

Step 3: Decide what stays and what goes. Some of what they’re doing might not be appropriate for their role or pay grade. This is your chance to redistribute tasks fairly and make sure everyone’s working to their strengths.

Step 4: Write it up. Job title, who they report to, main purpose, key responsibilities (5-8 bullet points), skills and experience, hours and location.

Step 5: Agree it together. This isn’t something you impose on them. Review the draft together, make adjustments if needed, and both sign off on the final version.

Real Example: How This Works in Practice

One of my clients had exactly this situation with their workshop manager, “Steve.” Steve had been with them for two years, gradually taking on more responsibility as the business grew. When they finally sat down to write his job description, they discovered he was effectively doing three different jobs.

We reorganised his role to focus on what he was actually good at (and enjoyed), promoted him to Senior Workshop Manager with a pay rise, and hired an apprentice to handle the more basic tasks he’d been covering.

Steve was delighted - he finally felt properly recognised. The business benefited because they had clear accountability. And the new apprentice got a proper role with clear expectations from day one.

What If They’ve Been Doing Things Wrong?

This is the fear, isn’t it? What if you document their role and realise they’ve been doing half of it incorrectly, or not doing parts of it at all?

Here’s the thing: if someone’s been working without clear expectations for months, any performance issues are partly on you as the employer. You can’t hold them fully accountable for not meeting standards that were never clearly communicated.

Use this as a fresh start. Be clear about what you expect going forward, provide any training they need, and give them a reasonable time frame to meet the new standards. Most people respond well to clear expectations - they just want to know what success looks like.

The Benefits You’ll See Immediately

Once you’ve got proper job descriptions in place for existing staff:

• Performance conversations become easier. You both know what they’re supposed to be doing, so you can have productive discussions about how well they’re doing it.
• Role boundaries get clearer. No more arguments about whose job it is to do something - it’s either in the job description or it isn’t.
• Career development becomes possible. Hard to promote someone when you can’t define what they’re currently doing, let alone what they’d be doing next.
• Hiring gets simpler. Now you know exactly what gaps you have and what you need new people to do.

Don’t Overthink It

The biggest mistake I see business owners make is turning this into a massive project. You don’t need to rewrite everyone’s job description at once, and you don’t need them to be perfect.

Start with the people where role clarity would make the biggest difference - usually your longest-serving employees or anyone whose role has significantly evolved. Get those sorted, then work through the rest gradually. Before the 2027 changes kick in is exactly the right time.

Ready to Get Your HR Documentation Sorted?

Writing job descriptions is just the beginning. If you’re realising there are gaps in your HR processes - and let’s be honest, most SME owners have more than they’d like to admit - you don’t have to tackle it all alone.

This is exactly what The HR Toolbox was built for - my HR platform for small businesses, with contract and document templates, holiday and absence tracking and onboarding all in one place. Take a look at thehrtoolbox.co.uk.

In 90 days, you’ll have all your HR ducks in a row: proper job descriptions, clear processes, and the confidence to handle whatever people challenges come your way.

Want to know more? Book a free discovery call and let’s chat about how to transform your HR from overwhelming to organised.

Emma Armytage is The HR Goddess, providing practical, jargon-free HR support to UK SME owners. She helps business leaders manage their teams confidently while staying compliant - without the corporate fluff.