Side Hustle Tax Calculator UK 2025/26

Side Hustle Tax in the UK: Everything You Need to Know for 2025/26

Having a side hustle alongside a day job is increasingly common in the UK — from freelance writing and photography to tutoring, dog walking, dropshipping, and content creation. But most people are unsure how to handle the tax side. This guide walks you through everything, step by step.

Hobby vs Side Hustle: Do You Actually Owe Tax?

First things first: is it a hobby or a business? HMRC uses the "badges of trade" to decide. If you are regularly generating income with the intention of making a profit, you are likely running a business — even if it feels casual. One-off sales or genuinely occasional income from a hobby are generally not taxable. However, if you are consistently earning money, HMRC expects you to declare it.

The good news: the £1,000 trading allowance gives you the first £1,000 of self-employment income per year completely tax-free. Below this threshold, you do not need to tell HMRC anything.

How Tax Works When You Have a Day Job Too

This is where it gets important. Your income tax personal allowance (£12,570 in 2025/26) and rate bands apply to your total income — employment plus self-employment combined. If your day job already takes you into the higher-rate band (40% on income over £50,270), every pound of side hustle profit above that is taxed at 40%, not 20%.

Example: You earn £45,000 from your job. Your side hustle makes £10,000 profit. The first £5,270 of that profit is taxed at 20%, and the remaining £4,730 is taxed at 40% — because those pounds push your total income over the £50,270 higher-rate threshold.

National Insurance on Self-Employment Income

Self-employed people pay two types of NI — both calculated on your self-employment profits, separately from your PAYE NI on your employment income:

• Class 2 NI: £3.45 per week (£179.40/year) if your profits are over £6,725. Paid via Self Assessment, not weekly. Entitles you to State Pension and other contributory benefits.
• Class 4 NI: 9% on profits between £12,570 and £50,270, then 2% on profits above £50,270. This is in addition to your income tax.

Note: Your employee NI from your day job and your Class 4 NI from your side hustle are calculated independently. HMRC does not apply an annual maximum between the two — they are separate obligations. However, if your combined employment and self-employment profits are very high, you may overpay NI and can apply for a refund.

Registering for Self Assessment

You must register with HMRC for Self Assessment by 5 October following the end of the first tax year your side hustle trading income exceeds £1,000. The tax year runs 6 April to 5 April. So if you first earned over £1,000 from your side hustle in the 2025/26 tax year (ending 5 April 2026), you must register by 5 October 2026.

Registration is free and done online at gov.uk. You will receive a Unique Taxpayer Reference (UTR) number. Deadlines to remember:

• 5 October: Register for Self Assessment (first time)
• 31 October: File paper return
• 31 January: File online return AND pay tax owed
• 31 July: Pay second payment on account (if applicable)

Allowable Expenses: Reduce Your Tax Bill Legally

You can deduct any expense incurred "wholly and exclusively" for your side hustle. Common allowable expenses include:

Alternative: Claim the flat £1,000 trading allowance instead of individual expenses. This is simpler and better when your actual expenses are under £1,000. You cannot use both.

Payment on Account: The Surprise Many New Filers Face

If your Self Assessment tax bill exceeds £1,000, HMRC requires you to make "payments on account" — advance payments towards next year's bill. You pay 50% of your current year's tax in January and another 50% in July. This means your first Self Assessment payment can be up to 150% of your annual tax bill (100% for the year just gone plus 50% advance for next year). Budget for this — many first-time filers are caught off guard.

Should You Consider a Limited Company?

As a sole trader, all your profits are subject to income tax and NI. If your side hustle is generating substantial profits — typically over £30,000–£50,000 net — a limited company can start to offer tax advantages. A company pays corporation tax at 19–25%, and you can extract profits as dividends (taxed at 8.75% basic rate, 33.75% higher rate) rather than as salary subject to NI.

However, a limited company brings additional responsibilities: annual accounts, Companies House filings, a company bank account, and usually accountancy fees of £1,000–£3,000/year. For a small side hustle, these costs typically outweigh the tax savings. Use our Corporation Tax Calculator to model the numbers.

VAT: The £90,000 Threshold

VAT registration becomes mandatory if your taxable turnover exceeds £90,000 in any rolling 12-month period. Below this threshold, VAT registration is optional (though sometimes beneficial). Once registered, you must charge VAT at 20% on most services and goods, file quarterly VAT returns, and pay the VAT collected to HMRC. Most side hustlers are well below this threshold.

Keeping Records: What You Need

HMRC requires you to keep business records for at least five years after the Self Assessment filing deadline. Keep:

• All invoices you issue and receive
• Bank statements for your business account (or personal account with business transactions highlighted)
• Receipts for all expenses you claim
• Mileage log if claiming vehicle expenses
• Contracts, agreements, or emails confirming work done

Free tools like a simple spreadsheet work fine for basic records. Apps like QuickBooks, Xero, or FreeAgent (free with some bank accounts) make it easier as your income grows.

Frequently Asked Questions