Your first Self Assessment tax return as a UK tradesperson

Government Gateway, and the other sign-in

HMRC's sign-in page (opens in a new tab) says there are two ways into HMRC online services. Government Gateway is a user ID, up to 12 characters, and a password. GOV.UK One Login is an email address and a password. If you already use one of those for HMRC, you keep using it. A Government Gateway user ID is still the one for HMRC even if you have a GOV.UK One Login for a different government service.

If you have never used HMRC online services, that page says you select "Create new sign in details" when you sign in, even if you already have a GOV.UK One Login from somewhere else. The service then guides you to create Government Gateway or GOV.UK One Login details.

The filing page (opens in a new tab) says you sign in, and you also need the UTR. You do not have to finish the return in one sitting. You may be asked to prove your identity, usually with photo ID such as a passport or a driving licence. The filing page is where you sign in. Type the gov.uk address yourself. Do not follow a search result that is not that page, and do not type the user ID, the password, or the UTR into a chat.

The records the return is built from

HMRC's records guide (opens in a new tab) says a sole trader keeps records of business income and expenses, and records of personal income. If you do not prepare accounts, you record income and expenses for each tax year, 6 April to 5 April. From the 2024 to 2025 tax year, cash basis is the default. You record income when you receive the money, and expenses when you pay the bill. You opt out if you want traditional accounting, or if you cannot use cash basis.

What to keep (opens in a new tab) is all sales and income, all business expenses, VAT records if you are registered for VAT, PAYE records if you employ people, and personal income. Proof includes receipts for goods and stock, bank statements, sales invoices, till rolls, and bank slips. You do not send that pile in with the return. You keep it so you can work out the profit, and so you can show it if HMRC asks. The records have to be accurate, and you have to be able to pick out the business transactions.

You keep them (opens in a new tab) for at least 5 years after the 31 January submission deadline of that tax year. HMRC's example is a 2022 to 2023 return filed online by 31 January 2024, kept until at least the end of January 2029. The same count, for a return with a 31 January 2027 deadline, runs to at least the end of January 2032.

What you are allowed to deduct, before any receipt becomes a number on the return, is in the allowable expenses guide. A chat tool does not decide that a cost is allowable.

The self-employment pages

The page for this year's return (opens in a new tab) says self-employment income goes on supplementary pages: the short ones, SA103S, or the full ones, SA103F. If you file online, the service asks for that income in the return. You do not post the paper pages as well.

The short-pages publication (opens in a new tab) was updated on 6 April 2026 with the form and notes for 2025 to 2026. Those notes say you use the short pages if your turnover was less than £90,000, or would have been if you had traded for a full year. The publication page describes that as below the VAT threshold for the tax year. If those two lines ever read differently, use the notes for the year printed on the form.

The same notes say you use the full pages (opens in a new tab) if any of these apply:

• turnover was £90,000 or more, or would have been if you had traded for a full year
• you need to adjust the profit because the accounting period ended before 31 March 2026, was not 12 months long, or did not end in the tax year
• you have adjustment income because you changed your accounting basis
• you need to adjust profits chargeable to Class 4 National Insurance
• you were in the Managing Serious Defaulters programme during the year

A first year that started after 6 April is not, on its own, a reason for me to send you to the full pages. Read the second bullet against the accounting period you actually use. If none of those apply, the notes point you to the short pages.

The short notes also set out the £1,000 trading income allowance. Total receipts from self-employment and miscellaneous income of up to £1,000 are exempt and do not have to go on a return, unless they come from a connected party, or you still need a return for another reason. If you claim the allowance, you cannot also deduct allowable expenses. If the expenses are higher and you want to claim them, you do not claim the allowance. The notes say a subcontractor who wants CIS deductions back still completes the short pages in some cases where the receipts are £1,000 or less. Read that line before you skip the pages.

The 2026 tax return notes (opens in a new tab) say you fill in the self-employment pages if you worked for yourself, or you were a construction subcontractor, and the turnover that would be taxed from all of your businesses was over £1,000. Employment pages are a different section. Subcontract income does not go on an employment page.

CIS deductions on that first return

If a contractor took CIS off your pay, that money is an advance towards your tax. It is not an expense. HMRC's subcontractor page (opens in a new tab) says you record the total pay before deductions as income, and the total deductions as CIS deductions. HMRC takes the deductions off the tax. Anything still owed is paid by 31 January after the tax year. If a refund is due, HMRC pays it back. That page does not say how many weeks a refund takes.

On the 2025 to 2026 short notes, box 38 is the total CIS deductions contractors took from 6 April 2025 to 5 April 2026. You add them up from the payment and deduction statements. The notes say the full turnover still goes in before those deductions, and you do not send the statements with the return. If you have already had some of the deductions refunded, they still go in box 38, and the refund goes in the tax-refunded box on the main return. The online return asks for the same two figures: income before the deduction, and the CIS deductions. I am not going to pretend the screen uses the words "box 38".

Putting the net amount in as turnover, and the deduction in as an expense, counts the money twice and hides the gross. The route for a sole trader, a partner, and a limited company is in the CIS tax refund guide. The rate on the statement is in the CIS deductions guide.

The payments on account surprise, in year one

HMRC's payments on account page (opens in a new tab) says these are payments towards the next tax bill, including Class 4 National Insurance if you are self-employed. Each one is half the tax you owed last year. They are due by midnight on 31 January and midnight on 31 July.

On a first return there were no payments on account last year, so 31 January can be the whole tax for the year plus the first payment towards the next year. The second half is 31 July. HMRC's own example on that page is a £3,000 bill, with £4,500 due that January: the £3,000, plus £1,500 as the first payment on account. I am leaving the pounds as HMRC wrote them. It is their example, not a typical trade bill. The second £1,500 in the example was the following 31 July.

You do not make those payments if the tax you owed last year was less than £1,000, or you paid more than 80% of the tax you owed outside Self Assessment, for example through a tax code. The statement or the online account shows the figures if they apply. How to read them, and how to ask for a lower payment if the next bill will be smaller, is in the payments on account guide. If you reduce them and the bill is higher, HMRC charges interest on the difference. This page is not a reason to reduce anything.

Prompts for the receipts, and for the figures you check

These sort notes you already have. They do not decide what is allowable, and they do not file anything. Leave out a UTR, a National Insurance number, a Government Gateway user ID, a password, and a bank account number.

Turn these receipt and invoice notes into a list I can check for a UK sole trader tax year. UK English. One line per item. Use only the dates and pounds I type. Do not invent a supplier, a customer, or an amount. If a date or a figure is missing, write MISSING. Do not say a cost is allowable. Do not add tax or National Insurance.

Tax year (6 April to 5 April):
Accounting method I use, or "not stated": cash basis or traditional
Income notes:
Expense notes:

Check every line against the receipt or the bank statement. Then the totals, still without a filing decision:

Lay out these Self Assessment figures so I can check them. UK English. Use only the numbers I type. Do not change a number. Do not tell me what I owe. Do not tell me to reduce a payment on account. If a figure is missing, write MISSING.

Tax year:
Turnover, the pay before any CIS deduction:
Allowable expenses I have already added up:
CIS deductions from the contractor statements:
Payments on account already made, or "none":
What my own sum says is profit:

If the draft has written a total you did not type, delete it. The return uses the figures you have checked. The checklist is the tick-list for the 2025 to 2026 year. The weekly email is where I put the next date that is worth knowing about.