The True Cost of DIY Accounting (And When to Hire an Accountant)

The saving that does not always materialise

The appeal of DIY accounting is simple: if you do not pay an accountant, you keep that money.

But the calculation only works if everything else stays equal — and it rarely does.

The question is not just what you pay for an accountant. It is what you lose without one.

The time cost is bigger than you think

Bookkeeping, reconciling bank statements, chasing receipts, preparing your tax return, understanding what you can and cannot claim — this takes time.

For most sole traders and small business owners, it adds up to several hours a month. Around Self Assessment season, that can spike significantly.

If your time is worth £30, £50, or £80 an hour, the maths starts to shift quickly.

An accountant who charges £600 to £1,200 a year — roughly £50 to £100 a month — may be cheaper than what you are effectively paying yourself to do the same work, and almost certainly does it faster and more accurately.

The tax you did not realise you could save

This is often where the biggest difference lies — not in the accountant's fee, but in the tax that goes unclaimed.

Most self-employed people underclaim on allowable expenses. Not through dishonesty, but because they simply do not know what they are entitled to.

Common examples of legitimately claimable expenses that get missed:

• Use of home as office — a proportion of heating, electricity, broadband, and mortgage interest or rent
• Business mileage — 45p per mile for the first 10,000 miles in a personal vehicle
• Phone and broadband costs — the business-use proportion
• Professional subscriptions and memberships
• Training and courses directly related to your trade
• Equipment, tools, and software — often claimable in full under the Annual Investment Allowance
• Bank charges and interest on business borrowing
• Accountancy and professional fees themselves

If you are a basic rate taxpayer earning £40,000, claiming an extra £2,000 in allowable expenses saves you £400 in tax. At higher rates, the saving is larger.

A good accountant will ask the right questions to make sure you are not leaving money behind. That conversation alone can easily cover their fee.

HMRC penalties are automatic and they add up fast

One of the clearest costs of doing your own accounts is what happens when something goes wrong.

HMRC does not send a warning letter before charging a penalty. The fines are automatic.

For a late Self Assessment tax return:

• £100 fine — even if you owe no tax, even if you are one day late
• A further £10 per day after three months, up to £900
• A further £300 or 5% of tax owed after six months
• A further £300 or 5% of tax owed after twelve months

Late payment of tax also triggers interest and surcharges on top.

If you are also registered for VAT, missing a VAT return or payment has its own separate penalty regime.

An accountant who keeps your deadlines on track pays for themselves the first time they stop you missing a filing date.

Errors cost more than they save

A mistake on your tax return is not always obvious at the time. You may file in good faith and only find out there is a problem when HMRC opens an enquiry.

HMRC enquiries can be time-consuming and stressful even when there is nothing wrong. If there is an error — claiming something incorrectly, calculating profits wrong, misunderstanding the rules for a particular type of income — HMRC can collect unpaid tax plus interest and, in some cases, a behaviour-based penalty on top.

An accountant who prepares your return reduces the risk of errors that trigger enquiries in the first place. Many accountants also offer fee protection insurance that covers the cost of dealing with an HMRC enquiry if one is opened.

There are savings beyond the tax return

For people who are growing, there are often bigger savings to be found than just the annual tax return.

An accountant can help you think about:

Whether to incorporate as a limited company — for some people, this significantly reduces their overall tax and National Insurance bill. For others, the timing is wrong or the benefits do not outweigh the admin. An accountant can model the numbers for your specific situation.

How to pay yourself tax-efficiently — if you run a limited company, the combination of salary and dividends you take can make a meaningful difference to your tax bill each year.

Pension contributions — contributions into a pension reduce your tax bill. The interaction with your income, allowances, and business structure affects how much you can put in and what you save.

Capital allowances and relief claims — if you buy equipment, a vehicle, or invest in your business, the timing and method of claiming relief can change how much tax you pay and when.

None of this requires exotic planning. It is the kind of advice a good accountant gives routinely because they see the full picture of your finances.

When DIY accounting can work

To be fair, there are situations where managing your own accounts makes sense — at least for a time.

DIY accounting is more manageable when:

• Your income is simple and from a single source
• You have very few transactions each month
• You are comfortable with numbers and record-keeping
• You have time to stay on top of deadlines and rule changes
• Your income is low enough that the cost of errors and missed claims is limited

If all of those things are true, the cost of an accountant may not be worth it in the short term.

But most businesses grow beyond this point faster than expected. And the longer you wait, the more untangling there is to do when you do bring someone in.

When to bring in an accountant

There are clear signals that it is time to stop doing it yourself.

• You are regularly spending more than a few hours a month on bookkeeping and tax
• You are not confident what you can and cannot claim
• Your income is growing and your tax bill is becoming significant
• You are thinking about whether to incorporate as a limited company
• You have missed a deadline or received a letter from HMRC
• You have multiple income sources — employment, self-employment, rental income
• You are registered for VAT or about to reach the threshold
• You want to take more money out of the business in a tax-efficient way
• You are planning to take on staff or grow beyond just yourself

Any one of these is usually enough. Several at once, and the decision is clear.

What does an accountant actually cost?

For a sole trader with straightforward finances, annual accountancy fees typically range from around £500 to £1,500 a year, depending on the complexity of your affairs, the level of service, and who you use.

For a limited company director, fees are usually higher — commonly £1,000 to £2,500 or more — because there is more to do: company accounts, Corporation Tax returns, director Self Assessment, and year-round advice.

Some accountants charge fixed monthly fees. Others charge per job. Many offer a free initial consultation so you can understand what is included before committing.

When you are comparing the cost, it is worth asking not just what the fee is — but what is included, what the accountant will proactively tell you, and whether they will help you plan rather than just file.

Is it worth switching?

If you are currently managing your own accounts and are not sure whether you are getting the best outcome, a quick conversation with an accountant will usually tell you.

At Aurestone Advisory, we offer a free initial review. We will look at your current position, tell you honestly what we think you could save, and give you a clear idea of what it would cost to work together.

If the numbers do not stack up in your favour, we will tell you that too.