Side hustle Self Assessment for beginners

What counts as a side hustle for tax?

A side hustle is not a special tax category. Depending on what you are doing, money earned from freelance work, consulting, online services, casual jobs, reselling for profit or other trading activity may be self-employment or miscellaneous trading income.

HMRC explains that Income Tax can apply to profits from self-employment, including services sold through websites or apps. Selling your own unwanted possessions occasionally is different from buying or making items with the intention of selling them for profit.

Start with gross income, not profit, for the £1,000 test

The trading allowance is up to £1,000 a year for qualifying trading and miscellaneous income. If your annual gross qualifying income is £1,000 or less, you will often not need to tell HMRC about it, subject to the exceptions in HMRC guidance.

Gross income means the money received before deducting your business costs. This is an important distinction: spending £700 on stock and selling it for £1,200 gives gross trading income of £1,200, even though the amount left before other costs is much lower.

Trading allowance or actual expenses?

If qualifying receipts are above £1,000, HMRC allows eligible individuals to use the £1,000 trading allowance as an alternative way of calculating profit instead of deducting actual allowable expenses. You cannot normally use the £1,000 allowance and also deduct the same trade's actual expenses.

That means the better option depends on your costs. If your allowable business expenses are substantially more than £1,000, using the actual expenses may produce a lower taxable profit. If your costs are very small, the trading allowance may be simpler or more valuable.

When do you need to register for Self Assessment?

HMRC says people who need to complete a return and have not filed before must normally tell HMRC by 5 October following the end of the relevant tax year. For the 2025/26 tax year, the published registration date was 5 October 2026. Check the current Self Assessment registration guidance for your own year and circumstances.

Do not wait until January to work out whether you needed to register. As soon as your side-hustle income grows beyond the small-income rules, keep proper records and check HMRC’s eligibility tool.

What records should you keep?

HMRC says you need records that allow you to complete the return correctly. For a simple side hustle, that normally means keeping evidence of your income and relevant business purchases or expenses.

A separate business bank account is not always legally required for a sole trader, but keeping side-hustle money separate can make record keeping far easier.

• Invoices or records of money customers paid you
• Receipts and invoices for business costs
• Relevant bank or payment-platform statements
• Mileage or travel records where a claim depends on them
• Details of equipment bought for the business
• Copies of returns, calculations and HMRC correspondence

Income is not the same as taxable profit

A common beginner mistake is assuming tax is charged on every pound that arrives in the business account. For a normal sole-trader business using actual expenses, the starting point is generally business income minus allowable business expenses, producing profit.

Whether a specific cost is allowable depends on the tax rules and what the expense was for. Personal spending does not become deductible simply because it was paid from a business account, and mixed-use costs can require an appropriate business portion.

Your job and your side hustle are considered together for Income Tax

Having PAYE employment does not give the side hustle a separate Personal Allowance. Your different taxable income sources feed into your overall Income Tax position for the year.

For example, someone whose salary already uses their Personal Allowance and basic-rate band may pay tax on side-hustle profit at their marginal rate. The exact result depends on total income, pension contributions, tax region and other circumstances.

What are the main Self Assessment deadlines?

The normal online Self Assessment filing deadline is 31 January following the end of the tax year, and the tax due for that return is also normally payable by 31 January. HMRC’s deadline page gives the dates for the current filing cycle.

You do not need to wait until January to file. Submitting earlier tells you what you owe sooner and gives you more time to prepare the money.

• Tax year ends: 5 April
• Tell HMRC you need to file, where required: normally by 5 October
• Paper return deadline: normally 31 October
• Online return and balancing-payment deadline: normally 31 January
• Second payment on account, where required: normally 31 July

Why your first January bill can feel surprisingly large

Some people need to make payments on account towards the following tax year. HMRC says they are generally two instalments, each usually half of the relevant previous-year amount, due on 31 January and 31 July.

Payments on account are not required in every case. HMRC currently says they are not required where the previous Self Assessment tax owed was less than £1,000 or where more than 80% of the tax was already collected outside Self Assessment. Check your actual statement rather than assuming they apply.

This is why simply saving the amount you think relates to last year’s side-hustle tax can sometimes leave a new filer short in January.

Set aside tax as you get paid

A practical system is to move part of each side-hustle payment into a separate tax pot as soon as the money arrives. The percentage that is sensible depends on your salary, profit, National Insurance position, student loans, pension contributions and other income.

The pot is not the tax calculation itself. It is a budgeting tool that stops the eventual bill competing with money you have already mentally spent.

A simple first-year workflow

• Record every payment you receive from the side hustle.
• Keep evidence for business costs as you incur them.
• Track gross trading income so you know when the £1,000 threshold is relevant.
• Decide whether actual allowable expenses or the trading allowance is appropriate.
• Check whether you need to register for Self Assessment and do it before the relevant deadline.
• Estimate the bill and build a dedicated tax reserve.
• File earlier than January if you can, so the final amount is not a surprise.
• Check whether the calculation creates payments on account for the following year.

When should you get professional help?

A straightforward sole-trader side hustle can often be manageable without an accountant, but professional advice becomes more valuable as the situation gets more complex.

Consider getting help if you have multiple businesses, substantial equipment purchases, VAT questions, overseas income, partnership income, complicated expenses, losses, high income affecting allowances, or you are unsure how an activity should be treated for tax.