Step 3 of my Top 20 Tips for Small Business Start Ups is the one you don’t want to hear. You've got the idea, you've tested it, you're buzzing, and every Monday morning at your desk makes you want to storm out waving a resignation letter.
I do get it. I’ve been there. But unless you're certain you can afford to (or you’ve lost your job anyway), the safest way to start a business is alongside your job, not instead of it. It might feel slow, and be prepared for it to be tiring, but it gives your business the best chance of surviving its wobbly first year.
Why keeping your job is the smart move
• You still have a regular income. The rent or mortgage, the bills and the weekly shop don't care how your launch is going.
• You're less desperate. When you need every sale to survive, you end up taking on the wrong customers, undercharging and making rushed decisions. A salary means you can afford to say no.
• Mistakes are cheaper. Your first few months will teach you a lot, and some of it will be painful, if I’m honest. It's much better to learn that on a Saturday afternoon than with an empty bank account.
• You can build proof. A few months of real customers, real feedback and real figures makes everything easier later, from writing your business plan to applying for funding.
That said, a few practical things deserve your attention before you start. None of them are scary, but all of them are easier to sort out now rather than later. (And just saying, I'm not claiming to be an employment lawyer or a tax adviser, so use this as a starting point and check your own situation.)
1. Check your employment contract first
This is the big one. Dig out your contract and staff handbook and look for anything about second jobs, outside work or conflicts of interest. Contracts vary a lot: some ban other paid work entirely, some say you must ask permission first, and some say nothing at all. Where there is a clause, starting a business without following it could end up as a disciplinary matter.
Even if your contract is silent, here are some sensible ground rules:
• Don't compete with your employer. Employees generally owe their employer a duty not to, so if your business is in the same field, tread very carefully and get advice.
• Keep the two completely separate. Don't use your employer's time, laptop, phone, email, customer lists or confidential information for your business. Not even "just once".
• Think about telling them. Where permission is needed, ask for it in writing. Even where it isn't, being open with your manager can avoid awkward surprises later. Plenty of employers are perfectly relaxed as long as there's no clash.
2. Keep an eye on your working hours
I know you're probably thinking "I'll work whatever hours it takes!" But burnout is a real threat. And if we’re getting legal about this, under the working time rules, you should generally not work more than 48 hours a week on average, normally averaged over 17 weeks.
If you're working a full-time job and building a business in the evenings and weekends, it adds up faster than you think. Employers also have responsibilities here, which is one reason some will ask whether you have another job. Acas has more detail on the maximum hours an employee can work if you want to check how it applies to you.
3. Tell HMRC when you need to
Don’t let this catch you out. Money you earn from your business is your responsibility to report, not your employer's.
• You get a £1,000 tax-free trading allowance each tax year (6 April to 5 April). That's one allowance in total, covering all your side income, not one per side hustle, so would include things like selling on Vinted.
• If your total trading income goes over £1,000, you'll need to tell HMRC, and you'll most likely need to register for Self Assessment as a sole trader. Typically you need to register by 5 October following the end of the tax year in which you started trading.
• If you don't tell HMRC when you should, you could face a penalty and an unexpected tax bill.
The quickest way to find out where you stand is the free GOV.UK tool to check if you need to tell HMRC about additional income. HMRC's Help for Hustles pages explain it in plain English too. We'll cover tax in more detail in Step 19, but my advice is to keep a simple record of every pound coming in and going out from day one. It takes minutes a week and saves hours later.
4. Plan your time realistically
This ties in with Step #5 (Plan out your Timelines to Launch), because the biggest threat to a part-time start-up is rarely a lack of ideas. It's running out of energy.
Try this:
1. Do a quick time audit. For one week, jot down where your hours actually go. You'll probably find pockets you didn't know you had, like lunch breaks, commutes and the hour of doom scrolling after dinner.
2. Decide your "business hours". Maybe it's two early mornings, one evening and half a Saturday. Put them in your diary like appointments, and protect them. Talk to your family to ensure they’re on board with this too.
3. Batch similar jobs together. I’ve found I’m much more efficient if I work this way, rather than flitting between tasks. Do all your invoicing in one go, all your social media in another.
4. Allow slack. Things will definitely take longer than you expect. Especially if you’re learning new skills. They always do.
5. Build your runway
Even while you're employed, it's worth knowing exactly how much money you need to live on, because that tells you when you can safely go full-time on your business. Start Up Loans offers a free personal survival budget template, alongside business plan and cash flow templates, in its free start-up guides. It's the list of everything you must pay each month (housing, food, bills, transport, debts, childcare) with the nice-to-haves stripped out.
Once you have that number, I suggest building a savings buffer to cover a good few months of those essentials before you take the leap. Many people aim for somewhere between three and six months as a starting point, but the right figure depends on your circumstances and how confident you are about your first customers.
6. Decide your "leap" triggers
It's easy to say "I'll go full-time when it feels right". It's safer to decide in advance what "right" means. Write your own criteria down, for example:
My business has covered my personal survival budget for three months running
I have a pipeline of customers or orders for the next few months
My savings buffer is in place
I've set aside money for tax
I've got a plan for the first six months of full-time working
Your list will be different, but having it means you're deciding with your head, not just on a miserable Sunday evening.
And it doesn't have to be all or nothing. You could ask to drop to four days a week, move to part-time hours or take a career break, so your business grows while you keep some security. Everyone has a right to request flexible working. It's worth having that conversation with your employer.
7. Look after yourself
Running a job and a business at the same time is hard, and burnout is real. Give yourself proper rest, keep one evening or day a week completely free, and treat it as a sprint with planned breaks rather than an endless marathon. A tired you will make worse decisions, serve your customers less well and enjoy the whole thing a lot less. And enjoying it is rather the point let’s remember!
So what to do next
Remember, you don't have to do everything today! Try these:
• ☐ Find your employment contract and check for second job or outside work clauses
• ☐ Use the GOV.UK tool to check whether you'd need to tell HMRC about your side income
• ☐ Do a one-week time audit and block out your weekly "business hours"
• ☐ Download the personal survival budget template and work out your monthly essentials
• ☐ Write down your own "leap" triggers for going full-time
Want to talk it through?
If you're wrestling with when (or whether) to make the leap, I'd be happy to help you think it through. You can book a call with me here.
Next up in the series: Step #4, Write a Solid Business Plan. Don't worry, it's much less scary than it sounds.
