Accountants for Sole Traders and the Self-Employed UK 2026

Most sole traders do not strictly need an accountant for self employed status to file legally. HMRC built Self Assessment for one person to complete alone, and a straightforward self-employed income with no VAT registration and no staff is exactly the case it was designed for. A lot of self-employed people pay for an accountant anyway, and the reasons split into two kinds: structural ones, like crossing the VAT threshold or taking on an employee, and time ones, where filing your own return is legal but not how you want to spend a weekend.

This guide sets out what a sole trader actually needs, what self-filing costs against paying someone, and where accountants for sole traders stop being optional.

Every price below is pulled from our full UK accountant cost breakdown, verified against each firm’s own pricing page in August 2026. Every tax date and threshold traces to GOV.UK. Where a rule is genuinely unverified, such as Making Tax Digital start dates or National Insurance rates, this guide says so rather than guessing at a figure.

Do You Actually Need an Accountant for Self Assessment?

HMRC’s online Self Assessment system was built for a single person to file their own return, and a genuinely simple sole trader is exactly who it works for: one income stream, no employees, turnover well under the £90,000 VAT threshold, and expenses that are easy to categorise from a bank statement and a folder of receipts. If that describes your business, you can legally complete and submit your own return without paying anyone, and plenty of self-employed people do exactly that every year. Where it stops being straightforward is anything with more moving parts: mixed income sources, a car or home used partly for the business, stock, or a first year of trading where you are unsure what counts as an allowable expense. None of that makes DIY filing illegal. It just makes the return slower to get right, and getting it wrong costs more than an accountant’s fee in the long run.

The honest test is not how much you earn, it is how confident you are that your numbers are right before you press submit. A £50 one-off filing, covered below, exists precisely for people who want that confidence without committing to a monthly fee.

Most sole trader returns come down to the same handful of categories: turnover, materials and stock, travel, a proportion of home costs if you work from home, and any equipment or software bought for the business. If you can list those five things confidently for the year, self-filing is realistic. If you are not sure which of last year’s purchases actually count as an allowable expense, that uncertainty is the real cost driver, not the size of your income, and it is exactly what an accountant checks before anything gets submitted.

Self Assessment Deadlines Every Sole Trader Needs to Know

The current Self Assessment tax year runs 6 April 2025 to 5 April 2026. If you file on paper, that return is due by 31 October 2026. Almost everyone files online instead, and the online deadline is 31 January 2027, which is also the date any tax owed must be paid. If HMRC collects part of what you owe through a PAYE tax code, for example because you also have an employed job, the deadline to submit online for that route is 30 December 2026 instead. Some sole traders also make a second payment on account towards the following year’s bill, due by 31 July. Missing 31 January means an automatic late-filing penalty even if you owe no tax, so the deadline that matters most is the one you file by, not just the one you pay by.

Sole traders pay Class 2 and Class 4 National Insurance alongside Income Tax through the same Self Assessment return. HMRC calculates both automatically once you enter your profit figures, so there is no separate form or manual calculation to get right. An accountant does not remove this step, they just check the return before it goes in.

One-Off Filing vs a Monthly Retainer: What Each Costs

Sole traders choose between two pricing models. A one-off filing costs the least and buys exactly one thing: your return submitted correctly. Cheaper Accountant’s basic Self Assessment starts at £50 a year, and Taxez offers the same service from £59. A fuller sole trader filing service, still one-off, runs from £150 a year. The alternative is a monthly retainer, where The Accountancy Partnership starts at £24.50 a month and Mazuma runs from £38 plus VAT for its Basic tier up to £60 plus VAT for Premium. A retainer costs more over a year, £294 at the cheapest monthly rate against £50 for a basic one-off filing, but it buys ongoing access to someone you can ask mid-year, not just a submitted form in January.

Neither route is objectively cheaper, they answer different questions. If your only real cost driver is getting one form submitted correctly once a year, the one-off route wins on price every time. Our full accountant cost breakdown covers both models across every firm we’ve verified, including the limited company side if your business ever incorporates.

What a Retainer Actually Buys You

A monthly retainer covers more than the return itself. Depending on the firm, that typically includes bookkeeping support through cloud software, unlimited questions through the year rather than a once-a-year conversation, help categorising expenses as you go instead of reconstructing a year of receipts in January, and a faster response if HMRC ever queries something. Our guide to what an accountant actually does breaks each of those jobs down individually if you want to see what you’re paying for beyond the filing.

What a retainer does not remove is the underlying bookkeeping work. Firms that charge lower one-off fees usually assume you arrive with clean, organised records; firms charging a monthly rate are more likely to help you build those records as you go. Software that captures receipts and matches them to transactions automatically, covered in our spend management guide, narrows that gap either way, because a tidy set of records is cheaper to process under either pricing model.

The other thing a retainer buys is a second opinion before the fact rather than a correction after it. A one-off filing service reviews the numbers you hand over. A retainer relationship means you can ask, mid-year, whether a specific purchase is deductible before you make it, which is a different kind of value and one that is genuinely hard to price into a single annual fee.

When It Becomes Worth Paying for an Accountant

Four events tend to be where a self-filing sole trader starts paying for help. VAT registration is the clearest: once your taxable turnover passes £90,000 in any rolling 12-month period, quarterly VAT returns become compulsory, and most people find that filing cadence harder to manage alone than an annual return. Taking on your first employee is the second, because payroll adds a recurring, time-sensitive reporting obligation rather than a once-a-year job. Property income is the third, since landlord Self Assessment is priced and treated differently to standard sole trader income, and is covered separately below. Incorporating as a limited company is the fourth, because company accounts, a Corporation Tax return and a confirmation statement replace the single sole trader return with three separate filings.

None of these four force you to pay an accountant by law, except payroll’s reporting obligations, which most people find easier with dedicated software or a bureau. But each one adds enough complexity that the time saved usually outweighs the monthly fee. If growth is genuinely the trigger, whether that’s VAT registration or your first hire, it’s also worth checking whether cash flow rather than compliance is the real constraint. Self-employed business loans and invoice finance solve a funding gap; an accountant solves a filing one, and conflating the two wastes money on the wrong fix.

Landlords and Property Income Are Priced Differently

If you earn rental income alongside self-employment, or instead of it, that is filed as property income on Self Assessment, not as sole trader trading income, and accountants price it as a separate job. Cheaper Accountant’s landlord Self Assessment service starts from £125 a year, above its £150-a-year sole trader rate, reflecting the extra detail a property return requires around allowable expenses and finance costs. If you have both a sole trader business and a rental property, expect a quote that reflects both income sources, not one flat sole trader price stretched to cover the second.

Choosing Between a One-Off Filing and a Retainer

• Count how many questions you actually asked last year – if the honest answer is zero, a one-off filing at £50 to £150 probably beats a £294-plus retainer.
• Check how close you are to £90,000 turnover – if VAT registration is likely within the next 12 months, a retainer that already handles quarterly filing saves switching providers mid-year.
• Confirm what a “basic” filing excludes – a cheap one-off price can still leave you doing all the bookkeeping yourself before you hand anything over.
• Ask what happens after your first year – some monthly rates are introductory, and the renewal price is the one you’ll actually pay for longest.
• Compare named firms, not category averages – our best online accountants comparison lines up specific providers against each other rather than a generic price range.

If you are still unsure, start with the cheapest route that matches your situation: file it yourself if your affairs are simple, pay for a one-off filing if you want a second pair of eyes without a monthly commitment, and only move to a retainer once you have a genuine, recurring reason to ask someone questions between January deadlines.

Clara Wenslow

Finance & Business Services Editor

Clara analyses SME finance and procurement markets, covering business loans, invoice finance, payroll, and related B2B services. She ensures each comparison and guide is transparent and data-driven.

Reviewed by

Sarah Mitchell

B2B Commerce & Finance Reviewer