Do I Need an Accountant for Self Assessment? A Guide for London Sole Traders

If you’re self-employed, a landlord, or earn income outside of PAYE, you already know that HMRC requires you to file a Self Assessment tax return each year. What’s less clear — especially if you’re doing it for the first time — is whether you need an accountant for Self Assessment, or whether you can manage it yourself.

The honest answer is: it depends. Some people can file their own returns with no trouble at all. Others are leaving significant money on the table without realising it. In this guide, I’ll walk you through exactly when hiring an accountant for Self Assessment makes sense, and when you might be fine going it alone.

What Is Self Assessment and Who Needs to File?

Self Assessment is HMRC’s system for collecting tax from people whose income isn’t automatically taxed through PAYE. You must register and file a return if, in the last tax year, you were:

• Self-employed as a sole trader earning more than £1,000
• A partner in a business partnership
• A landlord receiving rental income
• Earning more than £100,000 through employment
• Receiving income from abroad
• Claiming Child Benefit while earning over £60,000
• Earning untaxed income from investments, savings, or dividends

Filing your return incorrectly — or missing the 31 January deadline for online returns — results in an immediate £100 penalty, with further fines mounting rapidly after that.

Can You Do Your Own Self Assessment Tax Return?

Yes — HMRC’s online system (Government Gateway) is designed to be accessible to members of the public. If your financial situation is genuinely simple, you may be able to manage your own return. This typically means:

• You have a single source of self-employment income
• Your expenses are straightforward and clearly allowable
• You have no rental income, foreign income, or capital gains to declare
• You’re not VAT-registered
• You’re comfortable using online government systems

When Does Hiring an Accountant for Self Assessment Make Sense?

Your tax situation doesn’t stay simple for long. As your business grows, so does the complexity of your return — and the cost of getting it wrong. Here are the situations where working with an accountant genuinely pays for itself.

1. You’re unsure what expenses you can claim

This is where most self-employed people lose money without knowing it. HMRC allows a wide range of business expenses to be deducted from your taxable profit — but knowing exactly which costs qualify, and how to calculate them correctly (particularly for home working and vehicle use), requires experience. A good accountant will typically save clients more than their fee in additional deductions alone.

2. You have multiple income streams

If you’re self-employed and employed, or self-employed and a landlord, your return becomes significantly more complex. Each income type has its own rules, allowances and relief options that interact with one another. Getting the interaction wrong can mean paying too much — or triggering an HMRC compliance check.

3. You’ve had a particularly good or bad year

A high-income year may trigger tax planning opportunities — pension contributions, timing of expenses, or incorporation considerations. A loss-making year can generate valuable tax relief that carries forward or back. An accountant ensures you don’t miss these opportunities.

4. You’re worried about an HMRC enquiry

HMRC has the right to investigate your return for up to 12 months after filing (longer if they suspect fraud). Returns prepared by a qualified accountant are less likely to trigger an enquiry — and if one is opened, having professional representation is invaluable.

5. Your time is worth more than the fee

Filing your own return, gathering records, understanding the rules, and dealing with HMRC’s system typically takes a full-time sole trader between 8 and 20 hours per year. For many business owners, that time is simply more profitably spent on their actual work.

“I thought I was saving money by doing my own return. My accountant found £2,800 of allowable expenses I’d missed in the first year alone. The fee paid for itself many times over.”

Client testimonial, East London

What Does a Self Assessment Accountant Actually Do?

When you work with an accountant for your Self Assessment, the process is typically straightforward:

1. You provide your records — bank statements, invoices, receipts, P60s, and any other relevant documents for the tax year
2. Your accountant reviews everything — identifying all allowable expenses, reliefs, and deductions applicable to your situation
3. You review and approve the return — before anything is submitted to HMRC
4. Your accountant files directly with HMRC — on your behalf, before the deadline
5. You receive a clear summary — showing exactly what tax you owe and when to pay it

Key Self Assessment Deadlines for 2024/25

Deadline	What it applies to
5 October 2025	Register for Self Assessment (first-time filers)
31 October 2025	Deadline for paper tax returns
31 January 2026	Online return filing deadline + tax payment due
31 July 2026	Second payment on account (if applicable)

Missing the 31 January deadline results in an automatic £100 fine, rising to £900 after 3 months, and further daily penalties beyond that. Working with an accountant well before December avoids all of this entirely.

How Much Does a Self Assessment Accountant Cost in London?

The cost of hiring an accountant for a Self Assessment return in London varies depending on the complexity of your affairs. For a straightforward sole trader return, you should typically expect to pay between £150 and £350. More complex returns — with rental income, multiple income streams, or capital gains — will be higher.

Do I Need an Accountant for Self Assessment? The Bottom Line

If your income is simple, your expenses are clear-cut, and you’re confident using HMRC’s online system, you may well be able to handle your own return. But for most sole traders, landlords and self-employed professionals in London — especially those whose businesses are growing — working with a qualified accountant delivers better outcomes, lower risk, and genuine peace of mind.

As an accountant based in Dagenham, I work with clients across East London and beyond, handling everything from straightforward sole trader returns to complex multi-income situations. Every client receives a clear, transparent quote before any work begins.