Accountant vs No Accountant: What Does a Sole Trader Actually Save?

One of the most common decisions a sole trader faces is whether to hire an accountant or go it alone. The upfront cost of professional fees puts many people off. But when you add up what a good self assessment accountant actually does for you — and what going without one genuinely costs — the calculation is rarely as straightforward as it first appears.

This article breaks down the real numbers: what you pay for an accountant, what you save, and where the hidden costs of DIY bookkeeping tend to show up.

The Case for Doing It Yourself

Let's start with the argument for not using an accountant, because it's not entirely without merit.

HMRC's Self Assessment system is designed to be accessible. Most sole traders can log into their Government Gateway account, work through the online form, and file a return without professional help. For someone with very simple finances — a single source of income, minimal expenses, no property, no investments, no employees — this is genuinely achievable.

The self-employed accounting software market has also matured significantly. Tools like QuickBooks, Xero, FreeAgent, and various others can automate much of the bookkeeping, pull in bank transactions, and even pre-populate a tax return to some degree. If you're disciplined about keeping records and you're comfortable with numbers, DIY is a realistic option at the simpler end of the income spectrum.

The saving is obvious: sole trader accountant fees typically run from around £200 to £600 per year for a straightforward set of accounts and a self-assessment return. Why pay that when you can do it yourself?

The answer is in what you might be leaving on the table — and what risks you might be taking on without realising it.

What a Self Assessment Accountant Actually Does

A good accountant isn't just filling in the boxes on a tax return. Here's what's included in the work, even for a relatively simple sole trader:

Identifying allowable expenses you're missing. The HMRC guidance on what sole traders can and cannot claim as a business expense runs to hundreds of pages, and it's not always intuitive. Common areas where self-filing sole traders under-claim include: use of home as office, mileage, mobile phone and broadband costs, professional subscriptions, tools and equipment, marketing and advertising, training directly related to their trade, and bank charges. A good accountant will review your income and expenditure and prompt you to think about categories you might have overlooked.

Applying the right tax reliefs and allowances. The Personal Allowance, the Trading Allowance, the Marriage Allowance, Class 4 NIC treatment, and the interaction with any other income sources (rental income, dividends, PAYE employment) all need to be handled correctly. Errors here can mean paying too much — or potentially facing a penalty for underpaying. Note that Class 2 NICs are no longer charged for most self-employed people from April 2024 — those with profits above the Lower Profits Limit (£12,570) are treated as having paid them automatically, preserving State Pension and benefit entitlement without any payment required. However, those with profits below £6,725 may still wish to pay voluntary Class 2 NICs to protect their National Insurance record, and an accountant can advise on whether this is appropriate in your circumstances.

Getting the accounting basis right. From the 2024/25 tax year onwards, sole traders must use the "tax year basis" for their accounts, which replaced the previous "current year basis" following the Making Tax Digital reforms. Many sole traders who were on non-standard accounting periods have needed to deal with transitional adjustments. Getting this wrong leads to incorrect profit figures and incorrect tax bills.

Capital allowances. If you've invested in equipment, vehicles, computers, or other business assets, you may be able to claim capital allowances to reduce your taxable profit. The Annual Investment Allowance currently permits 100% deduction in the year of purchase on most plant and machinery up to £1 million. Many sole traders who file their own returns either miss these claims or apply them incorrectly.

Payments on Account planning. HMRC requires most sole traders to make Payments on Account — advance payments towards the following year's tax bill, made in January and July. Many first-time filers are shocked to receive a bill in January that includes not just their current year tax but also the first Payment on Account for the next year, effectively 150% of what they expected to pay. A good accountant will explain this upfront and help you plan your cash flow accordingly.

Preparing for an HMRC enquiry. HMRC opens enquiries into a proportion of self-assessment returns every year, chosen partly at random and partly based on risk indicators. If you're selected, you'll need to produce all the records and documentation supporting every entry on your return. An accountant will ensure you're keeping the right records from the outset, and will represent you if HMRC does make contact.

What Sole Traders Typically Save

It's impossible to give a universal figure, because it depends on your income, your industry, and how well you were keeping records before. But let's look at some concrete examples.

Example 1: A self-employed plumber earning £45,000 per year.

A sole trader in the trades often has legitimate expenses that are easy to under-claim: tools, materials, van running costs, mileage, workwear, phone, broadband, and professional body memberships. A common scenario is a trades person claiming only the most obvious expenses — materials and fuel — and missing several thousand pounds of additional allowable costs.

If a plumber earning £45,000 has legitimately allowable expenses of £12,000 but only claims £8,000 because they're not aware of all the categories, they're paying income tax and NICs on an extra £4,000 of "profit" that needn't be taxable. At the marginal rate applicable at that income level (20% income tax plus Class 4 NICs at 6%), that's approximately £1,040 in unnecessary tax. An accountant charging £400 per year has already paid for itself twice over — before considering time saved and peace of mind.

Example 2: A freelance designer earning £35,000.

A freelance designer working from home has valid claims for a proportion of their home running costs (heating, lighting, broadband, a proportion of rent or mortgage interest), equipment depreciation, software subscriptions, professional training, and any subscriptions to industry bodies or publications. They're also likely to have varying income month to month, which affects cash flow planning around tax payments.

Many designers in this situation either don't claim home office costs at all, or claim a flat rate that's lower than the actual allowable amount. Depending on the property, a properly calculated home office claim might add £500–£1,500 to allowable expenses — saving £100–£300 in tax. Add in other missed claims, and the saving from professional advice can easily outweigh the cost.

Example 3: A sole trader who's been over-claiming.

This scenario gets less attention, but it matters. Some sole traders, particularly those who've been self-filing for years, end up claiming expenses that aren't allowable — personal expenditure run through the business, excessive mileage claims, or costs that aren't "wholly and exclusively" for business purposes. An accountant will identify these and advise you to stop claiming them, reducing your risk of an HMRC enquiry and the penalties that can follow.

The Hidden Costs of DIY

The direct tax saving is only part of the story. There are several less-visible costs to doing your own accounts:

Your time. If you earn £20 per hour from your trade and you spend 15–20 hours per year on bookkeeping, receipts, reconciling bank statements, and completing your return, you've effectively spent £300–£400 of your working time. Time not spent on paid work is real cost.

Software. Good accounting software costs £15–£30 per month — £180–£360 per year. Many sole traders end up paying for accounting software and still spending significant time managing their records, which undercuts the "free" case for DIY.

Penalty risk. Filing a late return earns an automatic £100 penalty. Late payment of tax adds 5% penalties on top of interest charges. Making an error and under-reporting income can result in a further penalty based on the amount of tax understated, multiplied by a behaviour factor. These risks are manageable, but they're real — and they're higher when you're navigating a complex system without professional guidance.

Missed planning opportunities. An accountant doesn't just file your return — they have a conversation with you about your income, your plans, and your options. Are you considering taking on employees? Forming a limited company? Making pension contributions to reduce your tax bill? Buying equipment before or after the year-end to optimise your capital allowances? A good accountant will prompt these conversations at the right time.

Making Tax Digital for Income Tax: What's Changed From April 2026

This is the most significant change to self-assessment in a generation — and it has just come into force.

Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) came into effect from 6 April 2026, the start of the 2026/27 tax year. If you're a sole trader or landlord with total gross income above certain thresholds, the way you report your income to HMRC is changing fundamentally.

Who is affected and when:

• From 6 April 2026: sole traders and landlords with combined gross income from self-employment and property of more than £50,000 must comply
• From 6 April 2027: the threshold drops to more than £30,000
• From 6 April 2028: the threshold drops further to more than £20,000

If your income is above the relevant threshold, the annual self-assessment return is no longer the only obligation — it's replaced by a new regime of quarterly reporting.

What MTD for ITSA requires:

Instead of filing one annual return, you must:

1. Keep digital records using HMRC-recognised software
2. Submit four quarterly updates to HMRC during the tax year — broadly covering April–June, July–September, October–December, and January–March
3. Submit a final End of Period Statement after the tax year ends
4. Complete an annual tax return to crystallise the final tax position

The quarterly updates don't calculate your tax bill in real time — they're summaries of income and expenditure for the period. But they must be submitted digitally, on time, using compatible software. Late or missed submissions will trigger penalties under the new penalty points system.

What this means in practice:

For sole traders who've been managing their own accounts until now, MTD for ITSA is a step change in complexity. Four quarterly deadlines per year instead of one annual one. Mandatory digital record-keeping from day one of the tax year. Approved software required — HMRC's free tools do not currently support MTD for ITSA.

The case for getting professional support just got considerably stronger for anyone above the income threshold. An accountant can:

• Set you up on compatible software (such as QuickBooks, Xero, or FreeAgent — all of which have MTD-ready plans)
• Handle the quarterly submissions on your behalf so you don't need to track four separate deadlines
• Review each quarterly update before submission to ensure accuracy
• Plan around the quarterly figures so there are no surprises at year-end

If you're below the threshold:

If your self-employment income is below £50,000 (for 2026/27), you're not yet required to comply with MTD for ITSA. However, HMRC is gradually bringing everyone in. If you're close to the threshold — or growing — it's worth getting your record-keeping in order now, rather than scrambling to comply when the rules apply to you.

Even outside MTD, HMRC has signalled an expectation of more digital record-keeping across the board. Getting onto proper accounting software before you're required to is far less painful than being forced to change at short notice.

When DIY Makes Sense

To be fair, there are situations where DIY self-assessment is genuinely the right call:

• Your income is very simple: one source, minimal expenses, no property, no investments, no employees
• You're disciplined about keeping records throughout the year
• You're comfortable with numbers and happy to keep up with HMRC guidance as it changes
• Your income is at or below the threshold where an accountant's fee would represent a disproportionate cost (typically under £15,000 of trading income)

At lower income levels, the complexity is lower and the tax savings from professional advice are naturally smaller. A sole trader earning £12,000 from a side business alongside a PAYE job may find that self-filing is perfectly adequate.

When an Accountant Pays for Itself

At income levels above roughly £25,000–£30,000, the combination of higher tax stakes, greater expense complexity, and cash flow planning around payments on account generally makes professional advice worthwhile for most sole traders. At £40,000 and above, it's rare for the cost of a good accountant not to be recovered through better tax planning.

Beyond the numbers, there's also the question of where your time and energy is best spent. Most self-employed people went into business to do their trade, not to become part-time bookkeepers. The time you spend managing your own accounts is time you're not spending on your actual business.

Choosing the Right Accountant for a Sole Trader

If you're looking for a self assessment accountant, there are a few things worth checking:

Qualifications. Look for a qualified accountant — someone who is a member of ICAEW, ACCA, CIMA, or AAT. Unqualified bookkeepers can prepare accounts, but for tax advice you want someone with a professional body membership and the regulatory oversight that comes with it.

Fixed fees. A good accountant should be able to quote you a fixed annual fee covering your year-end accounts and self-assessment return. Hourly billing for straightforward sole trader work can lead to surprises.

Proactive communication. You want an accountant who gets in touch before deadlines, not after. Ask how they communicate with clients and how quickly they typically respond.

Relevant experience. An accountant who works regularly with sole traders in your industry will have a better feel for the common expenses, the industry-specific rules, and the planning opportunities that matter to your situation.

At Companies999, we provide accountancy services for sole traders, self-employed professionals, and small businesses across the UK. Our fixed-fee packages are transparent and cover everything from bookkeeping advice to your annual self-assessment return. Get in touch to find out more about our accountancy services, or take a look at our sector-specific pages for trades, freelancers, and other self-employed professionals.