Telling HMRC you work for yourself.

The £1,000 line, and the exceptions

Gross trading income over £1,000 in a tax year means you register for Self Assessment. Gross is before expenses. The trading allowance is what makes £1,000 the figure: at or under it, you may not have to tell HMRC, unless one of the exceptions applies. You still keep records of the income.

The exceptions are on the trading-allowance guidance, and they matter. You cannot rely on the allowance for income from a partnership, from your own company, or from your employer or your spouse or civil partner's employer. Other income has its own "tell HMRC" rules, including a band where you contact HMRC rather than registering, and a higher band where you register. Read that page if the only thing you have is a small amount of casual income plus something else. This guide is about a sole trade.

The deadline that is actually on the page

GOV.UK's registration page is written against the current filing season, not as a timeless sentence. Checked on 15 November 2026, it says you must tell HMRC by 5 October 2026 if you need to complete a return for the 2025/26 tax year and either you have not sent a return before, or you had registered before but did not need to send one for 2024/25. Telling them after that date can mean a penalty.

The pattern, which is what you need for a trade that starts later, is the 5 October in the tax year after the one you need to file for. A trade that starts in 2026/27 and needs a return points at 5 October 2027. The page itself will be updated with the next specific date. Use the page, not a memory of this sentence, when you are close to the day. You can register as soon as you start. Waiting until October is allowed. It is also how people miss it.

Registration is online. You will need your National Insurance number. HMRC posts a Unique Taxpayer Reference, the ten-digit UTR, and you cannot file without it. If you have had a UTR before and then dropped out of Self Assessment, the service may ask you to reactivate rather than start again. The page says you will be told which, inside the service.

What you have not done, by registering

• You have not registered for VAT. That is a separate test, at a much higher taxable turnover, explained in the VAT guide.
• You have not joined Making Tax Digital for Income Tax. That depends on gross self-employment and property income in an earlier year. Use the checker once you know those figures.
• You have not formed a company. A sole trader and a limited company are different legal things, and the tax is different.
• You have not set up a direct debit for Class 2. At or above the small profits threshold, Class 2 is treated as paid so that your National Insurance record is protected, and you do not pay it. Below the threshold it is voluntary. Class 4 is a percentage of profits over the lower limit, collected with the Self Assessment bill.

The take-home calculator shows Class 4 and the Class 2 position from the profit. It assumes that profit is your only income. If you also have a job, the Personal Allowance may already have been used by the job, and the calculator will overstate the allowance available to the trade.

Records from the first invoice

You do not need a limited company, and you do not need a particular brand of software, to be a sole trader. You do need a record of income and expenses. From 2024/25 the cash basis is the default: you record money when it comes in and when it goes out, unless you opt out or you cannot use it. Keep records for at least five years after the 31 January submission deadline for that tax year.

A sensible first year is dull. A separate bank account makes the record easier, though it is not the registration itself. Invoices with your name, a description and a date are enough to start. When the income is anything other than simple, or when you are about to hire someone, that is the point to pay an accountant rather than to stretch a calculator.