Self Assessment Tax Return for Tradespeople UK — A Complete Guide for Sole Traders (2026)

If you work for yourself in the trades — whether you're a sole trader electrician, a self-employed plumber, a CIS subcontractor, or the director of a small limited company — Self Assessment is a fact of life. HMRC requires you to declare your income, calculate what you owe, and pay it on time. Get it right and it's a manageable annual task. Get it wrong and you face automatic penalties, interest charges, and the anxiety of an HMRC enquiry. This guide covers everything you need to know for the 2025–26 tax year and beyond.

Who needs to file a Self Assessment tax return

HMRC requires you to file a Self Assessment return if any of the following applied to you in the tax year:

• You are a sole trader and your gross self-employment income was more than £1,000
• You are a partner in a business partnership (each partner files their own return)
• You are a director of a limited company — even if all your income was paid through PAYE, directorship alone triggers a Self Assessment obligation
• You are a director who takes dividends from your own company (dividends above the £500 annual dividend allowance must be declared)
• You are a CIS subcontractor who had tax deducted at source by contractors
• You had rental income from a property
• Your total income from all sources exceeded £100,000 (your Personal Allowance starts to taper at this level)
• You or your partner claimed Child Benefit and your individual income exceeded £60,000 (the High Income Child Benefit Charge)

The £1,000 figure is the Trading Allowance. If your gross self-employment income is below this threshold you do not need to declare it. Above it — even if you make no profit after expenses — you must register and file.

Registering for Self Assessment

If you have never filed a Self Assessment return before, you must first register with HMRC. Registration is done online at HMRC.gov.uk. You will need a Government Gateway account — create one if you don't already have one — and your National Insurance number to hand.

Once you register, HMRC will send your Unique Taxpayer Reference (UTR) number by post. This typically arrives within 10 working days, though it can take longer at busy times of year. You cannot file your return without your UTR, so register as early as possible.

The registration deadline is 5 October following the end of the tax year in which you started trading. The UK tax year runs from 6 April to 5 April. So if you started working for yourself in, say, August 2025, the deadline to register is 5 October 2025. Miss this and HMRC may issue a penalty even before you have filed a single return.

Key dates and deadlines

The Self Assessment calendar has four dates that matter. Knowing them in advance — and setting reminders — is the simplest way to avoid automatic penalties.

Note that the 31 January deadline covers three things at once: filing, paying last year's tax, and paying the first advance for the coming year. This is why January can feel financially brutal for tradespeople who have not planned ahead.

Payments on account — the first-year shock

In your first year of Self Assessment, you pay your tax bill once, by 31 January. Simple enough. In your second year, HMRC introduces payments on account — advance payments towards the following year's bill. This is where many tradespeople get caught out.

Payments on account apply if your Self Assessment tax bill (excluding Class 4 National Insurance in some cases) is more than £1,000. When this threshold is crossed, HMRC requires you to pay:

• First payment on account: 50% of last year's tax bill, due 31 January
• Second payment on account: another 50% of last year's tax bill, due 31 July
• Balancing payment: the difference between what you paid on account and what you actually owe, due the following 31 January

In practice, a tradesperson whose first-year tax bill is £4,000 will face a January bill of £4,000 (last year's bill) plus £2,000 (first payment on account for year two) — a total of £6,000. This is entirely legal and expected, but it shocks people who have not budgeted for it.

The fix is to set aside around 25–30% of every payment you receive into a separate tax pot throughout the year. This covers both income tax and Class 4 National Insurance and means you are never scrambling for cash when January comes. If your income drops significantly in a year, you can apply to reduce your payments on account through your HMRC online account — but do this formally rather than simply not paying, or interest will accrue.

Allowable expenses for tradespeople

Your taxable profit is your income minus your allowable business expenses. Claiming every legitimate expense you are entitled to is the single biggest lever you have over your tax bill — and it is entirely legal. The rule is simple: an expense must be wholly and exclusively for the purposes of your trade.

The table below covers the main expense categories for UK tradespeople.

What you cannot claim

Equally important as knowing what you can claim is knowing what HMRC will reject:

• Client entertainment: taking a client for a meal or drinks is not allowable, even if business is discussed
• Travel between home and a permanent workplace: ordinary commuting is not a business expense. However, site-to-site travel (between two client jobs in a day) is allowable, as is travel to a temporary workplace
• Ordinary clothing: jeans and a T-shirt worn on site are still personal clothing; they are not allowable even if you only wear them for work
• Personal proportion of mixed expenses: if your mobile phone is 60% business and 40% personal, only 60% is claimable — not the full bill
• Fines and penalties: parking tickets, speeding fines, HMRC penalties — none of these are deductible
• Capital repayments on a loan: interest on a business loan is allowable, but the repayment of the principal is not

The Trading Allowance

If your gross self-employment income is under £1,000 in a tax year, you can use the Trading Allowance instead of calculating individual expenses. You simply declare the income and deduct the full £1,000 allowance — no receipts needed.

In practice, the Trading Allowance is almost never useful for working tradespeople. If you are earning enough to do trade work regularly, your actual allowable expenses will far exceed £1,000 — meaning claiming real expenses will produce a much lower tax bill. The Trading Allowance is mainly relevant for very occasional odd-job income alongside regular employment.

Van costs: simplified mileage rate vs actual costs

One of the most frequently asked questions from tradespeople is how to claim for their van. You have two options, and you must pick one consistently for that vehicle:

Simplified mileage rate (HMRC flat rate): you claim 45p per mile for the first 10,000 business miles in the tax year, then 25p per mile for every mile above that. No receipts for fuel or servicing needed — just a mileage log. This is straightforward but often underestimates the real cost of running a working van.

Actual costs: you claim all real costs — fuel, insurance, road tax, servicing, repairs, MOT, tyres, finance interest. If the van is used exclusively for business, you claim 100% of these costs. If there is any private use (weekend trips, personal errands), you must apportion and only claim the business percentage. Most tradespeople with a dedicated work van that stays at the yard or job site can claim 100%. You must keep receipts for everything.

For most working tradespeople driving 15,000–30,000 business miles per year, actual costs usually produce a larger deduction. But the mileage rate is simpler to administer, especially if your record-keeping is not meticulous. Run the numbers for your situation, pick one method, and stick with it.

Record keeping — what HMRC expects

HMRC requires you to keep business records for at least 5 years after the 31 January filing deadline for the relevant tax year. In practical terms, if you file your 2024–25 return in January 2026, keep those records until at least January 2031.

The records you need to retain include:

• Invoices and receipts for all business income
• Receipts and invoices for all business expenses
• Bank statements covering business transactions
• Mileage log if claiming vehicle costs (date, start point, destination, purpose, miles driven)
• CIS deduction statements from contractors (if applicable)
• Purchase invoices for capital equipment claimed via AIA

Digital records are perfectly acceptable — photos of receipts, PDF invoices, exported bank statements. Those within HMRC's Making Tax Digital (MTD) pilot must keep digital records from the outset. Regardless of whether you are in MTD, using accounting software or at minimum a well-organised spreadsheet is strongly recommended. The discipline of keeping records throughout the year is what makes Self Assessment a one-hour task rather than a week-long ordeal in January.

A separate business bank account is not a legal requirement for sole traders, but it makes record-keeping dramatically simpler. When all business income and expenses flow through one account, reconciliation takes minutes. Mixing business and personal transactions in the same account creates unnecessary work and increases the risk of missing something.

Penalties for late filing and late payment

HMRC's penalty system is automatic. You do not get a warning letter first — the penalty is applied the moment you breach a deadline.

• Day 1 late (filing): £100 fixed penalty, regardless of whether you owe any tax
• 3 months late: £10 per day, up to a maximum of £900 (90 days)
• 6 months late: the greater of £300 or 5% of the tax due
• 12 months late: a further £300 or 5% of tax due (higher in cases of deliberate withholding)
• Late payment: interest accrues from the day after the deadline at the HMRC late payment rate (around 7.5% in 2026). A 5% surcharge is added after 30 days, another 5% after 6 months, and a further 5% after 12 months

Penalties for late filing apply even if your return shows no tax is owed. There is no minimum tax bill below which the £100 penalty does not apply. File on time, even if you cannot pay immediately — you can set up a Time to Pay arrangement with HMRC for the tax owed, but the late filing penalty cannot be undone.

Using an accountant — is it worth it?

For straightforward sole trader situations with a single income stream and clear expenses, many tradespeople file their own Self Assessment without difficulty. HMRC's online portal is reasonably well-guided and there is plenty of free help on gov.uk.

However, a qualified accountant adds real value in several situations:

• Your business is growing and you are approaching the VAT registration threshold
• You have a mix of income types (self-employment plus PAYE, CIS, dividends, rental)
• You are considering incorporating as a limited company
• You have had a good year and want to make sure you are claiming everything you are entitled to

The typical cost for a sole trader accountant in the UK is £300–£800 per year, depending on complexity and location. That fee is itself a fully allowable business expense. At turnover above £40k–£50k, an accountant almost always pays for itself in legitimate expenses identified and claimed, in tax-efficient structuring advice, and in the time saved. Below that level it is more of a judgment call based on your own confidence with numbers and record-keeping.

If you do use an accountant, your records still need to be in order. An accountant can only work with what you give them. Disorganised records mean more time (and higher fees) spent reconstructing the year, and a greater chance that legitimate expenses get missed because the receipts are not there to back them up.

The bottom line

Self Assessment is not complicated, but it rewards organisation. The tradespeople who find it stressful are almost always those who have left record-keeping to chance throughout the year and then face a scramble in January. The ones who find it manageable are those who keep clean records, set aside tax money monthly, and file early.

Register on time. Keep every receipt. Know your deadlines. Claim everything you are legitimately entitled to. Set aside roughly 25–30% of income as you go. Do those five things and Self Assessment will never be a crisis.