Finance Guide for Side Hustles

The £1,000 trading allowance

HMRC lets every UK adult earn up to £1,000 of gross self-employed income in a tax year (6 April to 5 April) without tax, registration or a tax return. This is one of the most useful provisions in UK tax: it covers the dog walking, the occasional freelance gig, the few hundred pounds of Etsy sales. If your gross side income — before any expenses — is under £1,000, you can stop reading and carry on.

Cross the £1,000 line and you must register for Self Assessment and declare the income. You can still choose to either deduct your actual expenses or use the £1,000 trading allowance instead of expenses — whichever leaves you with the lower taxable profit.

When and how to register

Registration is free, takes about 10 minutes, and is the single most common thing people put off too long. The penalty for filing late is £100 even if the tax owed is zero, with bigger penalties stacking from three months onward.

Keeping money separate

You are not legally required to have a separate account for side income — but mixing it with your salary makes year-end calculations painful and increases the chance of double-counting or missing deductible expenses. Open a free business account (Tide, Starling Business) or a separate personal account dedicated to the side hustle. Send all customer payments there and pay all hustle-related costs from it.

How a side hustle is taxed alongside a job

Your side-hustle profit is added on top of your salary and other income to determine your marginal tax rate. If your salary already uses up your £12,570 personal allowance — which most full-time salaries do — every pound of side-hustle profit is taxed from the first pound. The rate depends on your total income:

What you can deduct

The same "wholly and exclusively" rule applies as for full-time self-employed people. Common deductions for side hustlers include: software subscriptions, materials, equipment used for the side hustle (apportioned if dual-use), use of home (£6/week simplified), mileage for hustle-related travel at 45p/mile up to 10,000 miles, marketing, and a proportion of phone and internet costs.

Compare your actual expenses against the £1,000 trading allowance each year — many side hustlers find the flat £1,000 deduction beats itemising in their first year or two.

When the hustle outgrows the job

The decision to quit the job and go full-time on the hustle is more financial than emotional. Stress-test the numbers: can the hustle pay your full personal outgoings for at least six months while you absorb the lost employer pension contribution, sick pay, holiday pay and PI cover that comes with employment? Most successful transitions happen when the hustle is generating at least 80% of net salary for three consecutive months, with three months of personal cash reserves.