How do I file my UK limited company's Corporation Tax return and Companies House accounts without an accountant in 2026?
Since HMRC's free filing service closed, filing your Company Tax Return and your Companies House accounts without hiring an accountant means using commercial software that can handle both legs from your own figures. Below is the step-by-step procedure, plus the simplest and cheapest compliant route, what it actually costs, the deadlines that apply, and when professional advice is the better choice instead.
It depends on your company's complexity
For a straightforward trading or dormant company, where the director can prepare accurate profit and loss and balance sheet figures, self-filing both the CT600 and the Companies House accounts using suitable commercial software is generally the simplest and lowest-cost compliant route. You pay only for the software or filing fee, rather than a separate professional preparation fee, and can complete both legs from one set of figures.
Where the position is more complex — group relief, chargeable gains, R&D claims, loans to participators, charity or CASC status, or multiple supplementary pages — professional advice from a qualified accountant may be the more appropriate choice, even at a higher cost, because the risk and cost of getting a complex return wrong usually outweighs the fee saved by self-filing.
This page deliberately avoids quoting general "accountant fees typically cost £X" market benchmarks, since we could not verify a consistent, current, sourced figure across the profession. Where we cite a cost, it is WeFile's own live, published price, clearly labelled as one example rather than a market-wide average.
HMRC's free CT600 filing service has closed — here's what changed on 1 April 2026
The joint HMRC and Companies House online service for filing annual accounts and a Company Tax Return together — commonly known as CATO — closed on 31 March 2026. From 1 April 2026, Company Tax Returns generally need to be filed using commercial software; HMRC no longer offers its own free online filing route for the CT600.
A paper Company Tax Return is only accepted in narrow circumstances — for example where the company has a reasonable excuse for not filing online, or is filing in Welsh — so in practice almost every company now needs commercial software to file a CT600.
This closure affected the joint HMRC/Companies House route specifically. Companies House itself retained separate ways to file annual accounts — including its own web filing service, other approved software, or paper filing, subject to its normal rules — so the Companies House accounts obligation and the HMRC Company Tax Return obligation now run through different routes, even though the underlying figures overlap.
WeFile appears on HMRC's Corporation Tax commercial software suppliers list and on Companies House's software list for unaudited small company accounts — this confirms technical filing capability, not an endorsement or accreditation from either body.
For the authoritative detail, see GOV.UK's official closure guidance . We also cover this in more detail in our article on HMRC's free CT600 filing tool closing on 31 March 2026.
The Company Tax Return package
Form CT600
The Corporation Tax return form itself, including company details, the accounting period, income, profits, reliefs, the tax calculation, and a declaration confirming the information is correct and complete.
Relevant supplementary pages
Where they apply — for example CT600A for loans to participators (section 455 tax) or CT600E for charities and CASCs. Not every company needs supplementary pages.
Company accounts
Statutory accounts supplied to HMRC, normally in Inline XBRL (iXBRL) format, alongside a Corporation Tax computation showing how accounting profit is adjusted to arrive at taxable profit. Suitable software can generate these accounts, the tax computation and the CT600 itself from one set of figures — see our guide on how auto-generated filing documents work.
Filing deadlines
The Company Tax Return is normally due 12 months after the end of the accounting period, while any Corporation Tax owed is normally due 9 months and 1 day after the period ends — two separate deadlines worth tracking independently.
For a plain-English walkthrough of the whole return, see our Company Tax Return guide.
Step-by-Step: How to File Your CT600 and Companies House Accounts Without an Accountant
Suitable commercial software can generate both filings from one set of figures — but the two legs are still submitted, and accepted, separately.
Prepare accurate bookkeeping and accounts figures
Reconcile your bookkeeping records so your profit and loss account and balance sheet are accurate and balance correctly. These figures underpin both the statutory accounts and the Corporation Tax computation, so errors here carry through to everything that follows.
Choose suitable commercial filing software and confirm your company and accounting period
Since HMRC no longer offers its own free filing service, pick commercial software able to handle your company's account type (for example micro-entity, small company, or dormant accounts). Confirm the exact accounting period you're filing for — this is a common source of rejected or duplicate filings.
Complete your statutory accounts, CT600 and tax adjustments, then generate iXBRL accounts and computation
Enter capital allowances, disallowable expenses and other tax adjustments once. Suitable software then produces the CT600 form, the Corporation Tax computation, and — where applicable — iXBRL-tagged accounts, from that single set of figures.
Enter your genuine HMRC and Companies House credentials and review the documents and tax calculation
You'll need your own HMRC Government Gateway user ID and password, your genuine 10-digit Corporation Tax UTR, and — if filing accounts too — your company's Companies House authentication code. Review the automatically calculated tax figure and the generated documents carefully before authorising anything.
Submit from one workflow, tracking HMRC and Companies House as separate submissions
Submit your CT600 and, where applicable, your Companies House accounts from one workflow — but treat them as two separate submissions. Each has its own acceptance response and its own filing deadline, and any Corporation Tax owed must still be paid to HMRC separately from either filing.
WeFile is listed on HMRC's Corporation Tax commercial software suppliers list and by Companies House for unaudited small company accounts , and submits the Companies House leg through its own presenter account. These listings confirm technical filing capability — they are not an accreditation, approval, certification or endorsement from either body. Not every company can, or should, self-file this way: charity and CASC filings, and filings for entities without a Companies House number, are CT600-only, and companies with complex tax positions may still be better served by professional advice. If a submission is ever rejected, our guide explaining what HMRC's CT600 rejection codes actually mean can help you understand and fix the error.
iXBRL-Tagged Accounts: What UK Companies Need to Know
iXBRL stands for Inline eXtensible Business Reporting Language. It's an ordinary, human-readable HTML document — you can open it and read it like any web page — but it has machine-readable tags embedded inside it that identify each figure (turnover, profit, tax due, and so on).
HMRC requires company accounts and tax computations submitted with a Company Tax Return to be supplied in iXBRL, because it lets the same document be read by a person and processed automatically by HMRC's systems. Commercial CT600 software normally generates the required iXBRL automatically from the figures you enter, so you don't need to produce it by hand.
For the official technical explanation, see GOV.UK's XBRL guide for UK businesses .
CT600 and Companies House: two separate filings, three separate deadlines
HMRC and Companies House run separate deadlines and separate penalty regimes — they should never be treated as the same obligation. See our full Corporation Tax deadlines and penalties guide for a complete breakdown.
| Filing | Normal deadline |
|---|---|
| Companies House accounts (subsequent years) | 9 months after the financial year-end |
| Corporation Tax payment | 9 months and 1 day after the accounting period ends |
| Company Tax Return (CT600) | 12 months after the accounting period ends |
| Companies House first accounts | Generally 21 months after incorporation |
Worked example: accounting period ending 31 March 2026
- Companies House accounts due: 31 December 2026
- Corporation Tax payment due: 1 January 2027
- CT600 / Company Tax Return due: 31 March 2027
Make sure payment actually reaches HMRC by the deadline — if the date falls on a weekend or bank holiday, pay in good time using a method that clears before then. Companies with more complex arrangements, such as large companies paying by instalments, follow different rules.
HMRC late Company Tax Return penalties
For returns with a filing date on or after 1 April 2026:
| How late | Penalty |
|---|---|
| 1 day late | £200 |
| 3 months late | Another £200 (£400 fixed penalty in total) |
| 6 months late | 10% of unpaid tax |
| 12 months late | Another 10% of unpaid tax |
Repeated failures to file on time can increase the fixed penalties further. See GOV.UK's official CT600 late-filing penalty guidance .
Companies House late accounts penalties (private company)
These are entirely separate from HMRC's penalties above and apply to late statutory accounts.
| How late | Penalty |
|---|---|
| Not more than 1 month | £150 |
| More than 1, up to 3 months | £375 |
| More than 3, up to 6 months | £750 |
| More than 6 months | £1,500 |
The penalty is doubled if accounts are filed late in two successive financial years. See GOV.UK's official Companies House late-filing penalty guidance .
Who qualifies to file their own CT600 using software?
A company director may file the Company Tax Return themselves or appoint an agent to do it for them — but the director remains legally responsible for the return being accurate and filed on time, whichever route is chosen.
Being a micro-entity or small company does not, by itself, prove you're equipped to self-file, and it isn't a legal test of CT600 eligibility — those size categories determine which accounts regime applies at Companies House, not whether your tax affairs are simple enough to prepare yourself. See how WeFile detects and lets you choose your account type for more on how this works in practice.
| Criterion | Micro-entity (at least 2 of 3) | Small company (at least 2 of 3) |
|---|---|---|
| Turnover | £1 million or less | £15 million or less |
| Balance sheet total | £500,000 or less | £7.5 million or less |
| Average employees | 10 or fewer | 50 or fewer |
Before self-filing, make sure you can prepare accurate figures — our guide on filling in the balance sheet and profit and loss reports walks through the process step by step.
Certain companies are excluded from these regimes regardless of size (for example some financial services or group entities), and a company usually needs to meet the conditions for two consecutive years to change category. Always confirm your own position using the official guidance: GOV.UK company accounts criteria , Company Tax Return obligations and director responsibilities .
Even a company that comfortably meets the micro-entity or small company thresholds may still have tax affairs that call for professional advice — for example loans to participators, group relief, chargeable gains, or charity/CASC status. None of these examples make self-filing unlawful; they're simply situations where getting a second opinion is often worthwhile before you submit.
Related compliance reading: VAT is a separate tax regime from Corporation Tax with its own rules and deadlines — if your company is VAT-registered, see our Making Tax Digital for VAT guide for how MTD VAT compliance works alongside, but separately from, your CT600 obligations.
Comparing the compliant filing routes
| Route | Best suited to | Indicative cost |
|---|---|---|
| Self-file with commercial software (dormant) | Dormant companies with no trading activity in the period | … with WeFile (example, live price) |
| Self-file with commercial software (trading) | Straightforward trading companies where the director can prepare accurate figures | … with WeFile (example, live price) |
| Accountant-prepared and filed | Complex tax positions, group structures, or where you want professional sign-off | Varies by firm — request a quote directly; we don't quote a market average |
See a broader supplier comparison, including published prices and VAT treatment for other commercial software, on our Best CT600 Filing Software in 2026 page.
Is self-filing the right choice for your company?
- You can prepare an accurate profit and loss account and balance sheet, or have bookkeeping records that support them.
- Your company is dormant, or trading with a straightforward tax position (no group relief, chargeable gains, or complex reliefs).
- You're comfortable reviewing the automatic tax calculation and understand which supplementary pages, if any, apply to you.
- If your company has a close-company loan to a participator, charity/CASC status, group losses, or anything you're unsure how to report, consider getting professional advice before you file — even if it costs more upfront.
Why WeFile is a practical replacement for the closed service
WeFile is commercial software that guides a company director through preparing a profit and loss account and balance sheet (including dormant accounts), automatically calculates Corporation Tax, and can file both the CT600 and, for supported account types, the Companies House accounts from the same workflow. See the latest WeFile filing updates for what's changed recently.
WeFile appears on HMRC's Corporation Tax commercial software suppliers list and is listed by Companies House for unaudited small company accounts . This confirms supported electronic filing capability — it is not an accreditation, approval, certification, recommendation or endorsement from either body, and WeFile is not a like-for-like replacement for the closed government service: it is one commercial supplier among several, and it does not support every CT600 supplementary page or every accounts presentation.
WeFile supports the CT600A supplementary page (loans to participators / section 455 tax) and the CT600E supplementary page (charities and Community Amateur Sports Clubs), alongside detailed capital allowances and tax-adjustment handling. It does not support CT600B–D or CT600F–P, and charity, CASC and non-Companies-House entity filings are CT600-only — the Companies House accounts leg must be handled separately for those entities.
Frequently asked questions about CT600 filing after March 2026
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