Invoicing before
you register

Plenty of people land their first paying customer before they have told HMRC anything. That is fine. Registering as self-employed is about your tax, not about your right to send an invoice, and the law gives you time to do it. The risk is forgetting.

You can invoice straight away

An invoice is a request for payment. The legal requirements for it, a unique number, your name and address, the customer's details, a description, dates, amounts and the total, have nothing to do with whether you have registered yet. Your first invoice can go out the day you finish your first job. The guide on what a UK invoice must include has the checklist.

When you must register

If you need to complete a tax return, you must tell HMRC by 5 October after the end of the tax year in which you started. Tax years run from 6 April to 5 April. So if your first invoice is in June, you have until 5 October of the following year. If you tell HMRC later than that, you could get a penalty.

Registering for Self Assessment as a sole trader gives you a Unique Taxpayer Reference, which you then use for your returns.

The £1,000 trading allowance

If your trading income is £1,000 or less in a tax year, the trading allowance usually means you do not need to tell HMRC or pay tax on it. Once your trading income goes over £1,000, you need to register and report it. If you have more than one trade, the £1,000 covers them all together.

What your first invoices should show

Use your own name, and a business name if you have chosen one; if you trade under a business name, give an address where legal documents can reach you. Do not add a VAT number: you are almost certainly not VAT registered yet, and you must not charge VAT until you are. Start your invoice numbering properly from the first invoice; the invoice number generator sets up a format you can keep for years.

Keep records from day one

Your first invoices are part of your first year's records, and you will need them for your first tax return. Keep a copy of every invoice, a record of every payment and every business receipt. You must keep records for at least 5 years after the 31 January submission deadline of the tax year they relate to.

Working out your first tax bill

Your first return covers your profit for the tax year: income less allowable expenses. The sole trader tax calculator estimates the income tax and National Insurance, so you can put money aside from your first invoices rather than meeting the bill in one go the following January.

Side income alongside a job

Many people start self-employment alongside a salaried job. The same rules apply: you can invoice immediately, the trading allowance covers the first £1,000 of trading income, and above that you register and report your profit on a Self Assessment return. Your employer does not need to be involved.

A checklist for your first invoice

Choose your name or trading name. Set up invoice numbering. Agree the price and payment terms with the customer in writing. Send the invoice and keep a copy. Put a reminder in your diary to register for Self Assessment in good time before 5 October after the tax year ends. That is all it takes to start properly.

Your first year, date by date

For someone who sends their first invoice on 15 June 2026, in the 2026 to 2027 tax year:

Why the first bill can be bigger than expected

That long gap before your first tax payment is useful, but it hides a trap. When your first bill arrives on 31 January, it can include the tax for your first year and a first payment on account towards the next, which can be up to half as much again. Many new sole traders are caught out. Put a share of every payment aside as it arrives. The sole trader tax calculator estimates the income tax and National Insurance on your profit so you can pick a sensible percentage.

Starting properly from the first invoice

A few decisions made at the start save work for years:

• Your name and trading name. Decide whether you trade as yourself or under a business name, and use it consistently. See how to invoice as a sole trader.
• Numbering. Set up a format you can keep; the invoice number generator shows options.
• Payment terms. Decide your standard terms and put them on every invoice as a date; see invoice payment terms.
• Where payments go. Decide whether to use a separate account; see bank accounts for invoicing.
• Record keeping. Keep every invoice and receipt from day one; see how long to keep invoices.

Trading allowance or real expenses?

The £1,000 trading allowance is a choice as well as a threshold. If your trading income is more than £1,000, you can deduct the allowance instead of your actual expenses when working out your profit. That helps if your expenses are very low. If your real expenses are higher than £1,000, deduct those instead. You cannot do both. The trading allowance definition explains the rules, and the sole trader tax calculator applies whichever is better for you.

Side income and Making Tax Digital

If you start self-employment alongside a job, your employment income is taxed through PAYE and your self-employed profit through Self Assessment. Making Tax Digital for Income Tax applies once your qualifying income, from self-employment and property combined, passes the threshold for your year. Qualifying income does not include your salary, so a small side business alongside a job is often well below it. The MTD requirement checker tells you whether and when it applies.

A worked example

Priya starts making wedding cakes in June 2026 and sends her first invoice on 15 June. By the end of the tax year on 5 April 2027 she has invoiced £9,200 and spent £2,100 on ingredients, equipment and packaging. Her trading income is well over £1,000, so she registers for Self Assessment in the summer of 2027, comfortably before the 5 October deadline, and receives her Unique Taxpayer Reference. Her profit is £7,100. She has a part-time job, so her Personal Allowance is already used by her salary, and her cake profit is taxed at the basic rate. She files online by 31 January 2028 and pays the tax then. Because she kept every invoice and receipt from her first sale, the return takes an evening, not a week.

What if you missed the deadline?

If you should have registered by 5 October and did not, register now. Telling HMRC late can bring a penalty, and the longer the delay, the more likely that becomes. Keep your invoices and receipts in order in the meantime, so you can file quickly once you have your reference. It is always better to register late than not at all.

Common questions

Can I invoice under my own name before choosing a business name? Yes. You can add a business name later; just keep your own name on your invoices when you do.

Should I wait to register until I have more work? You can register as soon as you start, and doing so early avoids forgetting the 5 October deadline.

Do I need to tell my customers I am newly self-employed? No. Your invoice needs the standard details, not your registration status. What your customers care about is a clear invoice with a number, a description, the amount and a due date, the same as from any established business.

Will HMRC know about invoices I sent before registering? Your first return covers the whole tax year, including income from before you registered. Report all of it; registering later does not change which income counts.

Can I use invoice software before I register? Yes. Invoicing tools do not need a tax reference, and starting with one means your first year's records are already organised when you do register.

The short version

Send the invoice, keep the records, set money aside, and register with HMRC well before 5 October after the tax year ends. The paperwork follows the business, not the other way round, but it has to follow.

Start as you mean to go on, and the first January tax bill will be a date in the diary rather than a shock.