If you’ve started selling on Whatnot—whether it’s a side hustle or a full-time gig—one of the first questions you’ll face is: do I need to register as self-employed?
The short answer: probably yes. But there are exceptions, deadlines, and penalties to be aware of. In this guide, we’ll walk you through exactly when you need to register with HMRC, what happens if you don’t, and how the £1,000 trading allowance works.
When Do You Need to Register as Self-Employed?
In the UK, you must register as self-employed with HMRC if you’re earning money from self-employment—including selling on Whatnot—and your income exceeds certain thresholds.
The £1,000 Trading Allowance
The good news: if your total self-employed income (before expenses) is £1,000 or less in a tax year, you don’t need to register or file a tax return. This is called the trading allowance, and it’s designed to help casual sellers avoid unnecessary admin.
Important: This £1,000 limit applies to your total self-employment income, not just Whatnot. So if you also drive for Uber, sell on eBay, or do freelance work, it all counts towards that £1,000.
If You Earn Over £1,000
Once your self-employment income goes over £1,000, you need to:
- Register as self-employed with HMRC
- File a Self Assessment tax return each year
Even if your profit (income minus expenses) is below the Personal Allowance (£12,570 for 2024/25), you still need to register and file a return.
When Should You Register?
You must register with HMRC by 5th October following the end of the tax year in which you became self-employed.
Example Timeline
- You start selling on Whatnot in September 2024
- The tax year ends on 5th April 2025
- You must register by 5th October 2025
However, if you start self-employment after 5th October, you have three months from the date you started to register.
Our Advice: Register Early
Don’t wait until the deadline. Register as soon as you know you’ll exceed £1,000. It’s free, takes about 10 minutes online, and means you won’t risk missing the deadline.
What If You’re Already Employed?
You can be employed and self-employed at the same time. Plenty of Whatnot sellers have day jobs and run their shows in the evenings or weekends.
If this applies to you, you’ll still need to register as self-employed for your Whatnot income. HMRC treats employment income and self-employment income separately (though they’re both taxed together in your Self Assessment return).
What Happens If You Don’t Register?
Failing to register as self-employed is taken seriously by HMRC. Here’s what could happen:
1. Automatic Penalties
If you miss the 5th October deadline, HMRC can issue automatic penalties:
- £100 if you’re up to 3 months late
- Additional daily penalties of £10 per day (up to 90 days) if you’re 3+ months late
- Further penalties of £300 or 5% of the tax due (whichever is higher) at 6 and 12 months
2. Interest on Unpaid Tax
Any tax you owe will accrue interest from the date it was due until you pay it.
3. HMRC Investigation
If HMRC discovers you’ve been trading without registering, they can investigate your finances and potentially go back up to 20 years if they suspect deliberate tax evasion.
4. No “I Didn’t Know” Defence
Ignorance isn’t an excuse. HMRC expects you to understand your tax obligations, and “I didn’t know I had to register” won’t get penalties waived.
How to Register as Self-Employed
Registering is straightforward. Here’s how:
Step 1: Set Up a Government Gateway Account
If you don’t already have one, create a Government Gateway account at gov.uk. You’ll need:
- Your National Insurance number
- A UK address
- A phone number
Step 2: Register for Self Assessment
Once logged in, select “Register for Self Assessment” and choose “self-employed” as your reason.
You’ll be asked:
- When you started self-employment
- What your trade is (e.g., “online retail” or “reseller”)
- Your business name (if you have one—otherwise, just use your own name)
Step 3: Receive Your UTR
Within 10 working days, HMRC will post you your Unique Taxpayer Reference (UTR). This is a 10-digit number you’ll use to file your tax return.
Keep it safe—you’ll need it every year.
What About National Insurance?
Once you’re registered as self-employed, you’ll also need to pay National Insurance contributions on your profits.
There are two types:
Class 2 NI
- Paid if your profits are £12,570 or more per year
- Currently £3.45 per week (£179.40 per year)
- Collected automatically through your Self Assessment
Class 4 NI
- Paid on profits between £12,570 and £50,270: 6%
- Paid on profits over £50,270: 2%
- Also collected through Self Assessment
If your profits are under £12,570, you can choose to pay Class 2 NI voluntarily to maintain your National Insurance record (which protects your state pension and benefits). It’s optional, but often worth it.
Do You Need a Business Bank Account?
Legally, no—you can run your Whatnot business through your personal bank account. But we don’t recommend it.
Why open a separate business account?
- Makes record-keeping much easier
- Keeps personal and business spending separate
- Looks more professional
- Required if you register as a limited company later
Most banks offer free business accounts for sole traders, so there’s no reason not to.
“But I’m Just Selling My Own Stuff…”
This is a common question. If you’re genuinely just having a clear-out—selling your old clothes, collectibles, or household items—HMRC may not class that as trading.
But if you’re:
- Buying items specifically to resell
- Running regular live shows
- Making consistent profits
Then you’re trading, and the self-employment rules apply.
Grey area? If you’re unsure, it’s better to register. HMRC would rather you register unnecessarily than not register when you should have.
Do You Need an Accountant?
You don’t legally need an accountant to register as self-employed or file a tax return. You can do it yourself using HMRC’s online portal.
That said, an accountant can:
- Make sure you’re claiming all allowable expenses
- Maximise your tax efficiency
- Handle the paperwork so you can focus on selling
- Advise on when to consider a limited company
For many Whatnot sellers, the tax savings an accountant finds more than cover the cost of the service.
Key Takeaways
✅ You must register as self-employed if your Whatnot income exceeds £1,000 per tax year
✅ Register by 5th October after the tax year you started trading
✅ Even if you have a full-time job, you still need to register for your Whatnot income
✅ Penalties start at £100 and increase the longer you delay
✅ Registration is free and takes about 10 minutes online
Need Help Getting Set Up?
At Simplr Accounting, we help Whatnot sellers get their tax affairs in order from day one—from registration to Self Assessment, bookkeeping, and tax planning.
Not sure if you need to register? Get in touch and we’ll talk you through it.