Before You Register as Self-Employed With HMRC

From the trading allowance to record-keeping, here is what to check before you tell HMRC you are self-employed, so your first Self Assessment return holds no surprises.

Summary

• If your gross self-employed income goes over £1,000 in a tax year, HMRC expects you to register for Self Assessment by 5 October after that tax year ends.
• The trading allowance covers up to £1,000 of side income per tax year with no tax or National Insurance, and one allowance covers all your side hustles combined.
• Registering gives you a Unique Taxpayer Reference, which you need to file; the improved online service now issues it within 72 hours.
• The online return and any tax owed are due by 31 January after the tax year ends; paper returns must reach HMRC by 31 October.
• Keep records of sales, income and costs from the start, even if an accountant files for you, and set money aside for tax as you earn.

Earning money on the side brings a handful of tax jobs that are easy to put off. The rules themselves are not complicated, but the dates and paperwork catch people out, and HMRC can charge penalties and interest on tax that goes unreported. This checklist runs through what to sort out before you register as self-employed, from deciding whether you need to register at all to setting up records and habits that make your first return manageable.

First Check: Do You Need to Register at All?

Work through these questions before anything else. If you are unsure, HMRC has a free online checker tool on GOV.UK that tells you what, if anything, you need to do next.

• Your gross self-employed income went over £1,000 in the tax year. Gross means your total income before any costs. If so, HMRC expects you to register for Self Assessment.
• You received untaxed income over £2,500 from other sources. That also puts you in scope for Self Assessment.
• You earned under £1,000 but want to pay Class 2 National Insurance voluntarily. Registration is optional here, but it protects your entitlement to the State Pension and certain benefits.
• You are only selling your own unwanted possessions now and then. That is usually not trading, so you probably do not need to tell HMRC, though it is sensible to check.
• You already file a Self Assessment return for another reason. Do not register again. Report the new income on your existing return, though you may need to register separately for Class 2 National Insurance.

The Trading Allowance and Small Side Income

The trading allowance is a tax-free allowance of £1,000 per tax year for trading and casual income. If your gross income from all your side work combined is £1,000 or less, the allowance covers all of it: no tax, no National Insurance and normally no need to tell HMRC.

• The threshold is gross income, not profit. Earn £1,150 and spend £300 on materials, and you have still crossed it.
• One allowance covers every side hustle. Earning £800 from tutoring and £400 from selling crafts is £1,200 in total, so registration applies.
• Cash in hand counts the same as money paid straight into your bank account.
• You cannot use the trading allowance and deduct actual expenses against the same income. It is one method or the other, and with bigger incomes and genuine costs, actual expenses usually produce the lower taxable profit.
• The allowance rises from £1,000 to £3,000 from April 2027, announced at the Budget on 28 October 2026. The £1,000 limit applies until then.

What Registration Gives You: UTR and an Online Account

Registering for Self Assessment is how you tell HMRC you need to file a return. Several things follow once you have done it.

• You are issued a Unique Taxpayer Reference (UTR), the number you need to complete and file your return. Under the improved online registration service, it appears in your online account within 72 hours instead of taking up to 15 days to arrive by post.
• You sign up through your Personal Tax Account, using Government Gateway or GOV.UK One login details, and receive a confirmation email or text when registration is complete.
• HMRC sends you a notice to file each year until you tell them you have stopped. You do not register again every year.
• Once registered, you can get an estimate of the bill you might face and arrange regular weekly or monthly payments towards it.

Deadlines for Telling HMRC

The tax year runs from 6 April to 5 April. If you cross the £1,000 threshold in a tax year, HMRC expects you to register by 5 October following the end of that year. Exceed the limit during the 2026 to 2027 tax year, for example, and the registration deadline is 5 October 2027.

• Leave it later than 5 October and HMRC will still contact you about filing: they write with a revised date, three months counting from the date of that letter or email.
• The paper return must reach HMRC by 31 October after the end of the tax year. The online deadline is 31 January, which is also when the tax you owe must be paid.
• If you have PAYE income and want any tax collected through your tax code, you must file online by 30 December instead.
• If you make payments on account, instalments towards your bill, the second payment deadline is 31 July.

The practical steps for the return itself are covered in our walkthrough of how to file your first Self Assessment tax return.

National Insurance: Class 2 and Class 4 Basics

National Insurance is a second charge on self-employed income, separate from Income Tax. What applies depends on how much you make.

• Income covered by the trading allowance carries no National Insurance, as well as no Income Tax.
• If you earn £1,000 or less, you can pay voluntary Class 2 contributions. That is worth considering because it protects your entitlement to the State Pension and certain benefits.
• Once you are within Self Assessment, National Insurance on your profits is worked out through your tax return alongside Income Tax. The classes and amounts depend on your profits and change over time, so check GOV.UK for the current figures before you budget.
• If you still have a job, the National Insurance on your payslip continues as normal. Side income never appears on your payslip; telling HMRC is your responsibility, not your employer’s. Pension saving through a workplace scheme also continues separately under auto-enrolment, as our guide to workplace pensions and auto-enrolment explains.

Records to Keep From Day One

Keeping full and accurate records is your responsibility, even if you later hand everything to an accountant or tax agent. Start the habit before you register.

• Bank statements and receipts: HMRC points to these as the records you need so your return is filled in correctly.
• A running record of all sales and income, with dates and amounts.
• Receipts for business expenses, if you plan to deduct actual costs rather than claim the trading allowance.
• A note of any platform fees. Some selling platforms deduct their cut before the money reaches you, and your gross figure includes those fees, which matters for the £1,000 test.

Money Habits That Make the First Return Easier

Small routines now save a scramble in January.

• Keep the side income in a separate account, or at least a separate pot, so it never mixes with your wages.
• Set aside part of every payment for tax. A fixed amount moved each week or month turns one large bill into a series of small ones, the same smoothing method we describe in our guide to budgeting for UK household bills.
• Use HMRC’s estimator once you have registered to see roughly what the bill might be, then set up regular payments towards it.
• File your online return early rather than waiting for the deadline. It also cuts the risk of missing genuine HMRC messages among the fake ones: scammers pose as HMRC to get hold of money and personal details, so never follow links in unexpected messages and never share your sign-in details.

Next steps

• How to File Your First Self Assessment Tax Return: the full walkthrough of registering, records and filing once you have decided to register.
• Budgeting for UK Household Bills: a method for spreading irregular costs, which works just as well for tax bills.
• Workplace Pensions and Auto-Enrolment: how pension contributions work when you have a job alongside your self-employment.

Questions readers ask