“Should I hire an accountant?” is the question every sole trader reaches at some point — usually around the second week of January, when the Self Assessment deadline is looming and the return still isn’t done.

The honest answer is that it depends entirely on how complex your tax situation is, how much your time is worth, and how confident you are with HMRC’s rules. Some people are paying £300/year for an accountant when their return takes 20 minutes and the trading allowance covers everything. Others are wrestling with a spreadsheet at midnight, missing £2,000 in legitimate reliefs, and convincing themselves they’re saving money by doing it alone.

Here’s a framework for deciding, based on the actual complexity of your situation — not a generic “everyone should” or “nobody needs to.”

The 5-Question Self-Test

Before you even think about costs, answer these five questions honestly. Each one is a signal — not a verdict — but together they tell you whether your return is in “DIY in an afternoon” territory or “this needs a professional” territory.

1. How many income sources do you have?

One source — a single sole-trade business, or one PAYE job with some self-employment on the side — is straightforward. HMRC’s online service handles it cleanly.

Two or more changes the picture. If you have self-employment income plus rental income, or two different sole trades, or self-employment plus dividend income from a company, each source has its own section on the return, its own expense rules, and its own potential reliefs. Get the allocation wrong and you can overpay by thousands without realising.

Three or more — self-employment, property, dividends, foreign income, CIS deductions — and you’re in territory where an accountant will almost certainly save you more than they cost. The interaction between income sources affects your Personal Allowance taper, your payments on account, and your MTD qualifying income calculation.

2. Is your turnover above £50,000?

The £50,000 threshold matters for two reasons. First, it’s the point where Making Tax Digital for Income Tax becomes mandatory from April 2026 — which means digital record-keeping and quarterly updates, not just an annual return. Second, it’s roughly the level where the tax at stake is high enough that a single missed relief or misclassified expense can exceed an accountant’s annual fee.

Below £50,000 with simple expenses? DIY is realistic. Above £50,000, or approaching it, the complexity and the amounts involved both scale up — and so does the value of professional help.

3. Are you claiming anything beyond basic expenses?

If you’re claiming the £1,000 trading allowance and nothing else, your return is simple. If you’re claiming actual expenses — car costs, use of home as office, capital allowances on equipment — the rules get complicated quickly.

The moment you’re dealing with capital allowances, pension tax relief at the higher rate, Marriage Allowance, or benefits in kind, you’re making decisions that have a right answer and several expensive wrong answers. An accountant doesn’t just file — they check whether you’re using the right method.

4. Have you missed the deadline, or are you behind on multiple years?

If you’re reading this in January with the deadline days away and the return not started, an accountant can file quickly and correctly — and may be able to reduce penalties if you’re already late.

If you’re behind on multiple years, this is not a DIY job. Filing several years at once involves allocating income, losses, and payments on account across tax years in a way that’s easy to get wrong. An accountant can file all outstanding returns, negotiate with HMRC on penalties, and set up a Time to Pay arrangement if you owe a large amount. This is one of the clearest cases where professional help pays for itself.

5. Are you at risk of an HMRC investigation?

Certain situations increase the likelihood of an HMRC compliance check: undeclared foreign income, large expense claims relative to turnover, cash-heavy businesses, or inconsistencies between years. If any of these apply, having an accountant who knows your records and can respond to HMRC on your behalf is valuable insurance — not just for the investigation itself, but because well-organised records from the start reduce the risk in the first place.

Read our guide on what triggers HMRC investigations if you’re unsure whether this applies to you.

What an Accountant Actually Costs

Let’s be specific, because vague “it depends” answers aren’t helpful when you’re trying to decide.

One-off Self Assessment (sole trader)

  • Simple return (one income source, basic expenses): £150–£250
  • Moderate complexity (multiple income sources, property, reliefs): £250–£500
  • Complex / multiple years: £400–£800+

Ongoing (monthly retainer)

  • Sole trader bookkeeping + annual return: £50–£150/month
  • Limited company (accounts, CT600, payroll, bookkeeping): £100–£250/month
  • Complex company (VAT, multiple directors, CIS): £200–£400/month

Online tax return services

The key question isn’t “can I afford an accountant?” — it’s “is the time I’d spend doing this myself worth more or less than the fee?” If you bill clients at £40/hour and your return takes 5 hours, that’s £200 of your time — roughly the same as a simple accountant fee, except the accountant will also catch things you’d miss.

When DIY Is the Right Call

You don’t need an accountant if all of these are true:

  • One income source (a single sole trade or one self-employment alongside PAYE)
  • Turnover under £50,000 and not approaching the MTD threshold
  • Using the trading allowance or claiming only straightforward expenses (no capital allowances, no complex reliefs)
  • Up to date — no missed deadlines, no back years
  • Confident with the rules — you understand what you can and can’t claim, and you’re not guessing

If that’s you, HMRC’s online filing service is free and takes 20–40 minutes for a simple return. Our first-year self-employed checklist walks you through the process step by step, and our guide to the UK tax year covers the deadlines you need to hit.

You can also use accounting software to track income and expenses through the year, which makes the return itself much faster — even if you file it yourself.

When an Accountant Pays for Itself

You should seriously consider professional help if any of these apply:

  • Multiple income streams (self-employment + property + dividends + foreign income)
  • Turnover above £50,000 or approaching MTD mandatory registration
  • A limited company — Corporation Tax, director salary, dividends, and PAYE are not DIY-friendly
  • Behind on returns or filing late — an accountant can file multiple years and negotiate on penalties
  • Claiming capital allowances, pension relief at higher rate, or complex reliefs — the rules have expensive edge cases
  • You’ve received an HMRC letter — a compliance check, investigation, or enquiry is not something to handle alone
  • Your time is worth more than the fee — if 3+ hours of your time costs more than the accountant, the decision is made

The Middle Ground: Tax Return Services

There’s an option between “do it myself at midnight” and “hire a full-service accountant” — online tax return services. These are platforms where you upload your records, answer questions, and a qualified accountant (employed by the service) files your return. They cost £100–£300, sit between DIY and traditional accounting in price, and are designed for people whose returns are too complex to feel comfortable DIYing but not complex enough to justify a £500+ accountant.

We break down the exact differences — including when a service beats an accountant and when it doesn’t — in our tax return service vs accountant vs software comparison.

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