Filing CT600 Without an Accountant: Is It Safe? A Step-by-Step Guide

Filing CT600 Without an Accountant: Is It Safe? A Step-by-Step Guide

Every year, thousands of UK company directors ask themselves the same question: "Do I really need to pay an accountant to file my corporation tax return?"

It's a fair question. Accountants charge anywhere from £400 to £2,000+ for CT600 preparation and filing. If your company is simple — one director, straightforward income and expenses, no complicated structures — that's a lot of money for what might be a 20-minute job.

But is it safe to file without one? Will HMRC come knocking? Will you make an expensive mistake?

This guide gives you an honest answer — including when DIY filing makes perfect sense, when you should absolutely keep your accountant, and exactly how to do it yourself step by step.

The Honest Answer: It Depends on Your Company

Let's get straight to it. Filing your CT600 without an accountant is:

• ✅ Perfectly safe for most micro-entity limited companies with simple finances
• ⚠️ Risky for companies with complex structures, unusual transactions, or significant tax planning needs
• ❌ Not recommended for companies with multiple subsidiaries, overseas operations, or active HMRC enquiries

The key word is complexity. The CT600 itself isn't inherently difficult — it's a form that reports your company's profits and calculates the tax owed. For a simple company, most of the 100+ boxes don't apply to you.

When It's Safe to File Without an Accountant

You're a good candidate for DIY CT600 filing if your company ticks most of these boxes:

✅ Your Company Is a Micro-Entity

A micro-entity is the simplest type of limited company. You qualify if you meet at least two of:

• Turnover of £632,000 or less
• Balance sheet total of £316,000 or less
• 10 or fewer employees

Most one-person limited companies qualify easily. Micro-entities can file simplified FRS 105 accounts, which makes the whole process much more straightforward.

✅ You Have One Main Income Source

If your company earns money from one type of activity — consulting, contracting, freelancing, a small trade — the CT600 is simple. Your turnover goes in one place, your expenses in another.

It gets more complex if you have multiple income streams, investment income, rental property, or overseas income.

✅ Your Expenses Are Straightforward

Standard business expenses — office costs, equipment, travel, software subscriptions, professional fees, phone bills — are all allowable expenses that reduce your taxable profit. If that's the extent of your expenses, you're fine.

It gets complex when you need to split expenses between personal and business use, or when you have disallowable expenses that require adjustment in the CT600.

✅ You're a Sole Director With a Simple Salary + Dividends Setup

The classic contractor setup: pay yourself a small salary (usually around the NI threshold — typically £12,570 in 2025/26) and take the rest as dividends. This is straightforward for CT600 purposes.

✅ You Keep Good Records

If you use bookkeeping software like Xero, QuickBooks, or FreeAgent, and you keep your records up to date throughout the year, you have everything you need. The CT600 is essentially a summary of your annual figures.

If your records are a shoebox of receipts and a vague memory of what you earned, you might need an accountant to sort things out first.

✅ You're Comfortable With Basic Numbers

You don't need to be an accountant. But you need to be comfortable reading a profit and loss statement, understanding the difference between turnover and profit, and knowing what capital allowances are (equipment purchases you can deduct from taxable profit).

If you run your own company, you probably already have these skills.

Tick most of these boxes? You can file your CT600 with Taxpipe for £59 — no accountant required.

When You Should Keep Your Accountant

Be honest with yourself. There are situations where professional advice is worth every penny:

❌ Your Company Has Complex Structures

If you have subsidiary companies, a group structure, or you need to claim group relief, an accountant is essential. The CT600 supplementary pages for these situations require specialist knowledge.

❌ You're Claiming R&D Tax Credits

R&D tax relief can be extremely valuable — but the rules are complex and HMRC scrutinises claims closely. An incorrectly prepared R&D claim can trigger an enquiry. If you're claiming R&D, use a specialist.

❌ You Have Significant International Operations

If your company earns income overseas, has foreign subsidiaries, or deals with transfer pricing, you need professional advice. International tax rules are genuinely complex.

❌ You Have a Director's Loan Issue

If you've taken more money out of the company than you've put in (an overdrawn director's loan account), there are specific tax implications (Section 455 tax) that need careful handling. If you're not sure whether your director's loan is overdrawn, ask an accountant.

❌ You're Closing Your Company

Closing a limited company involves final accounts, potential capital distributions, strike-off or liquidation, and a final CT600. The tax implications of how you extract money from a closing company can be significant. Professional advice usually pays for itself here.

❌ HMRC Has Opened an Enquiry

If HMRC is enquiring into your return, get professional representation immediately. This isn't the time for DIY.

❌ You Have Significant Losses or Reliefs to Claim

Carrying losses forward or back, claiming marginal relief on complex structures, or dealing with capital allowances on significant assets (property improvements, expensive equipment) — these situations benefit from professional input.

❌ You're Just Not Confident

And that's absolutely fine. If the thought of filing your own tax return makes you anxious, and that anxiety would affect your daily life, paying an accountant for peace of mind is a valid choice. There's nothing wrong with knowing your limits.

The Real Risks of Filing Without an Accountant

Let's address the fears directly:

"What if I make a mistake?"

Everyone worries about this. Here's the reality:

Minor mistakes — a miscategorised expense, a small arithmetic error — are common even in accountant-prepared returns. HMRC's systems catch obvious errors, and you can amend your CT600 within 12 months of the filing deadline at no cost.

Significant mistakes — understating income, claiming expenses that aren't allowable, incorrect tax calculations — are more serious. But modern CT600 software (including Taxpipe) has built-in validation that catches most of these before submission. The software won't let you submit something that's obviously wrong.

Deliberate mistakes — fraudulently understating your income or inventing expenses — that's tax evasion, and no amount of accountant involvement protects you from that. (And an accountant won't help you do it either.)

"What if HMRC investigates me?"

HMRC doesn't investigate returns based on whether an accountant prepared them. They look for:

• Unusual patterns (sudden drops in income, abnormal expense ratios)
• Late filings or late payments
• Random selection
• Information from third parties (banks, other tax authorities)

A well-prepared DIY return is no more likely to trigger an enquiry than an accountant-prepared one. In fact, some HMRC officers have noted that self-prepared returns for simple companies are often more straightforward than over-complicated accountant-prepared returns.

"Will I miss a tax deduction?"

This is the strongest argument for an accountant. A good accountant might spot deductions you didn't know about — a capital allowance claim you missed, a relief you're entitled to, an expense you didn't realise was allowable.

However, for a simple micro-entity company, the potential missed deductions are limited. Read our guide on allowable expenses and you'll know what to claim. The vast majority of tax savings for simple companies come from basic, well-known deductions — not obscure reliefs.

"What if I file late?"

This is a risk whether you use an accountant or not. In fact, one common complaint about accountants is that they file late because they're busy with other clients.

When you file yourself, you control the timeline. You know your deadline, and you can file whenever you're ready — no waiting for your accountant to "get to your file."

CT600 penalties for late filing start at £100 and escalate over time. Filing on time is important regardless of who prepares your return.

Don't risk missing your deadline. File with Taxpipe — most directors complete the process in under 30 minutes.

Step-by-Step: How to File Your CT600 Without an Accountant

Here's the complete process. It's less scary than you think.

Step 1: Gather Your Information

Before you start, you need:

• Your company's UTR (Unique Taxpayer Reference) — a 10-digit number from HMRC
• Your accounting period dates — typically your financial year (e.g., 1 April 2025 to 31 March 2026)
• Your HMRC Government Gateway credentials — the login you use for HMRC online services
• Your financial summary for the period:
  • Total turnover/revenue
  • Total expenses (broken down by category is helpful)
  • Any equipment purchases (for capital allowances)
  • Any other income (bank interest, investment income)
  • Director's salary paid
  • Dividends paid

If you use accounting software (Xero, QuickBooks, FreeAgent), run a Profit & Loss report and a Balance Sheet for the period. That covers most of it.

Step 2: Choose Your Filing Software

Since HMRC's free filing service closed in March 2026, you need third-party software to file. Your main options:

For a first-time DIY filer with a simple company, Taxpipe is specifically designed for you. It's the most affordable option and the easiest to use.

Step 3: Enter Your Company Details

In Taxpipe, you'll start by entering:

• Your company registration number
• Your company name
• Your accounting period start and end dates
• Your company's registered address

Taxpipe verifies your company details against Companies House, so you can be confident everything's correct.

Step 4: Enter Your Financial Data

This is the main part. You'll enter:

Income:

• Trading turnover (your total revenue from business activities)
• Any other income (bank interest, one-off income)

Expenses:

• Cost of sales (if applicable)
• Staff costs (salaries, employer NIC, pension contributions)
• Office and premises costs
• Travel and subsistence
• Professional fees
• Marketing and advertising
• Equipment and tools
• Software and subscriptions
• Other business expenses

Capital Allowances:

• Business equipment purchased during the period
• Annual Investment Allowance (AIA) claims
• Full expensing claims (if applicable)

Other Information:

• Associated companies (if any — affects your corporation tax rate thresholds)
• Any brought-forward losses

Taxpipe guides you through each section with plain English explanations. If something doesn't apply to your company, skip it.

Step 5: Review the Tax Calculation

Taxpipe calculates your corporation tax automatically, including:

• Taxable profit after allowable deductions
• Corporation tax rate (19% for profits up to £50,000, 25% above £250,000, with marginal relief in between)
• Tax due — the amount you'll need to pay HMRC

Review this carefully. Does the taxable profit look right? Is the turnover correct? Are all your expenses included?

This is your sanity check. If something looks off, go back and check your figures.

Step 6: Submit to HMRC

Once you're happy with the figures, submit. Taxpipe files your CT600 directly to HMRC through their official API, along with:

• Your corporation tax computation
• Your iXBRL-tagged accounts (generated automatically)

You'll receive a confirmation from HMRC with a unique submission reference. Save this. It's your proof of filing.

Step 7: Pay Your Corporation Tax

Filing your CT600 and paying your tax are two separate things. After filing, you need to pay HMRC by the payment deadline (9 months and 1 day after your accounting period ends).

You can pay by:

• Direct bank transfer (fastest)
• Direct Debit
• Corporate credit/debit card
• HMRC online payment service

Make sure you use the correct payment reference — HMRC uses your company's UTR with the accounting period end date.

Step 8: Keep Your Records

After filing, keep all your supporting documents for at least 6 years. This includes:

• Bank statements
• Invoices (issued and received)
• Receipts for expenses
• Payroll records
• Your CT600 submission confirmation
• A copy of your accounts

HMRC can open an enquiry into your return for up to 12 months after filing (or longer if they suspect fraud), so having good records is important.

Ready to try it? Start your CT600 filing with Taxpipe — guided, validated, and done in about 20 minutes.

How Much Money Will You Actually Save?

Let's do the maths for a typical sole director of a micro-entity limited company.

The Accountant Route

Some accountants bundle these into a monthly retainer of £75–£150/month, which works out to £900–£1,800/year.

The DIY Route With Taxpipe

Potential saving: £541–£1,541 per year.

Over five years, that's £2,705–£7,705 — enough for a significant business investment, a healthy emergency fund, or simply more money in your pocket.

And if you're currently paying at the lower end (say £500/year), you're still saving £441 per year or £2,205 over five years.

See what it costs: Taxpipe pricing — £59, everything included.

Real Concerns Addressed

"But my accountant catches things I'd miss"

For a simple micro-entity, what would they catch? Your turnover is what it is. Your expenses are what they are. The corporation tax calculation is mathematical — software does it exactly right.

The "things you'd miss" argument makes more sense for complex companies with multiple reliefs, group structures, or unusual transactions. For a one-person company with one income source and standard expenses, there's very little to miss.

If you're worried, read our guides on allowable expenses and common CT600 mistakes before filing. That covers 99% of what an accountant would check for a simple company.

"My accountant gives me tax planning advice"

For simple companies, the main "tax planning" is:

1. Pay yourself the optimal salary — usually at the NI threshold (currently £12,570)
2. Take the rest as dividends — more tax-efficient than salary above the threshold
3. Claim all allowable expenses — use the complete list
4. Claim capital allowances — AIA for equipment purchases
5. Consider pension contributions — corporation tax deductible

That's it. You now know what most accountants tell their micro-entity clients. Is that worth £500+ per year?

"I don't have time"

Filing a CT600 for a simple company with Taxpipe takes about 20–30 minutes. Your accountant probably spends about the same amount of time on it — plus time chasing you for information, which they bill you for.

The time investment is:

• 10 minutes: gathering your figures from accounting software
• 15 minutes: entering them into Taxpipe
• 5 minutes: reviewing and submitting

Compare that to the time you spend emailing your accountant, sending them documents, waiting for questions, reviewing their work, and processing their invoice. DIY is often faster end-to-end.

"What if the rules change?"

CT600 software is updated when rules change. Taxpipe stays current with HMRC's requirements, including rate changes, new reliefs, and updated filing rules. You don't need to track changes yourself — the software handles it.

"I've been with my accountant for years — is it awkward to leave?"

Your accountant is a professional providing a service, not a friend you're breaking up with. If you decide to file yourself, simply let them know you won't need their services for CT600 filing this year. Many accountants understand this trend and won't take it personally.

Some directors keep their accountant on a "consultation only" basis — paying for advice when needed (perhaps an hour per year) rather than a full service retainer. This gives you the safety net without the ongoing cost.

A Sensible Transition Plan

If you're nervous about going fully DIY, here's a gradual approach:

Year 1: File Yourself and Get Your Accountant to Review

File your CT600 yourself using Taxpipe, then pay your accountant for a one-off review (typically £100–£200). They'll check your figures and let you know if anything looks wrong.

This gives you the experience of filing yourself with a professional safety net.

Year 2: File Yourself With Confidence

After seeing how straightforward it is (and getting your accountant's confirmation that you did it right), file independently. You can still call an accountant if something unusual comes up.

Year 3+: Full DIY

By now, you've done it twice, you know the process, and you're saving £500+ per year. The CT600 is just another annual admin task, like filing your confirmation statement at Companies House.

What About Companies House Annual Accounts?

The CT600 is your tax return for HMRC. You also need to file annual accounts at Companies House. These are two separate obligations.

For micro-entities, Companies House accounts are very simple — basically a short balance sheet. You can file them online through Companies House's own service, or through your accounting software.

Taxpipe generates iXBRL accounts as part of the CT600 filing process — these go to HMRC. Your Companies House accounts are a separate (simpler) version.

Tools That Make DIY Filing Easy

The right tools make all the difference:

With these tools, you have everything an accountant would use for a simple company — at a fraction of the cost.

The Bottom Line: Is It Safe?

Yes — if your company is simple. Filing your CT600 without an accountant is not reckless, irresponsible, or dangerous. Thousands of directors do it every year, and modern software like Taxpipe makes it easier than ever.

The CT600 is a structured form with well-defined rules. For a micro-entity limited company with one director, one income source, and standard expenses, there's nothing magical about what an accountant does. They enter your numbers into the same boxes, check the calculations, and submit to HMRC — exactly what Taxpipe does, but with guidance built in.

Know your limits. If your company has complexities — group structures, R&D claims, overseas operations, significant director's loan issues — get professional help. The cost of an accountant is trivial compared to the cost of getting complex tax wrong.

Start simple. If you've never filed before, your first CT600 is a great time to try DIY. The process teaches you about your company's tax position, and understanding your own tax return is valuable knowledge for any company director.

Take the first step. Sign up for Taxpipe and file your CT600 in about 20 minutes. It's £59, it's guided, and it's designed for directors exactly like you.

Frequently Asked Questions

Is it legal to file my CT600 without an accountant?

Absolutely. There is no legal requirement to use an accountant for your CT600. Any company director can prepare and file their own corporation tax return. HMRC's systems don't distinguish between accountant-prepared and self-prepared returns.

Will HMRC treat my self-filed return differently?

No. HMRC processes all CT600 returns the same way, regardless of who prepared them. Your return is filed through the same API whether you use an accountant, CT600 software, or (previously) HMRC's own filing service.

How long does it take to file a CT600 yourself?

With Taxpipe, most directors complete the process in 20–30 minutes — assuming your financial records are up to date. The most time-consuming part is usually gathering your year-end figures, not the actual filing.

What if I realise I made a mistake after filing?

You can amend your CT600 within 12 months of the original filing deadline. If you've overpaid tax, HMRC will issue a refund. If you've underpaid, you'll need to pay the difference plus any interest.

Do I need accounting qualifications to file a CT600?

No. You need to understand your company's basic financial position — turnover, expenses, profit — which you should know as a company director anyway. Taxpipe guides you through the process without requiring any accounting knowledge.

What's the most common mistake directors make when filing themselves?

Forgetting to claim allowable expenses — particularly capital allowances on equipment purchases, working from home costs, and pension contributions. Our guides cover all of these in detail.

Can I go back to using an accountant if DIY doesn't work out?

Of course. Filing your own CT600 one year doesn't commit you to doing it forever. Many directors try DIY filing, find it straightforward for their simple company, and never look back. Others prefer the reassurance of professional help. It's entirely your choice.

How much does an accountant typically charge for CT600 filing?

For a micro-entity limited company, typical accountant fees are £400–£1,500 per year for annual accounts and CT600 filing combined. Read our detailed cost comparison for more specific figures.

Is Taxpipe suitable for my first-ever CT600?

Yes — in fact, first-time filers are one of Taxpipe's primary audiences. The guided flow explains each step, and the built-in validation catches common errors. Read our first-time director's guide for additional context.

What if my company has more than one director?

Having multiple directors doesn't necessarily make your CT600 more complex. As long as the company qualifies as a micro-entity and has straightforward finances, Taxpipe can handle it. The CT600 is about the company's finances, not the number of directors.

Should I still use accounting software if I'm filing my CT600 myself?

Yes, absolutely. Good bookkeeping (using Xero, QuickBooks, FreeAgent, or similar) throughout the year makes CT600 filing dramatically easier. Your accounting software handles the day-to-day records; Taxpipe handles the annual tax return. They complement each other perfectly.

What records do I need to keep after filing?

Keep all financial records for at least 6 years from the end of the accounting period. This includes bank statements, invoices, receipts, payroll records, and your CT600 submission confirmation. Read our record keeping guide for the complete list.

Last updated: February 2026. Ready to file your CT600 without an accountant? Get started with Taxpipe — £59, about 20 minutes, no accounting knowledge required.

Related Reading

• How to File Your CT600 Yourself in 2026 (Complete DIY Guide)
• Accountant vs DIY CT600 Filing: Honest Comparison
• Accounting Periods Explained — When Does Your Corporation Tax Year Start and End?