# Filing Small Company Accounts in the UK: Rules and Deadlines

Learn how small UK limited companies file annual accounts to Companies House and HMRC, navigate the new iXBRL software rules, and prepare for upcoming P&L changes.

**Published:** 2026-07-14  
**Updated:** 2026-07-14  
**Source:** https://aztajournal.com/gb/filing-small-company-accounts-uk

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> Filing financial accounts for a small UK limited company requires submissions to both Companies House and HMRC. Understanding the latest iXBRL software rules, specific statutory size limits, and strict annual deadlines is essential to keep your business fully compliant and avoid penalties.

Every small UK limited company must submit financial accounts to both Companies House and HM Revenue and Customs (HMRC) to remain legally compliant. Under the **Companies Act 2006**, directors must file these documents annually, though the preparation rules and public visibility criteria differ between the two registries. Failing to navigate this dual-filing system will result in automated, non-negotiable financial penalties from both departments.

## Key Takeaways

1. **Dual Submissions**: Companies must prepare and submit statutory accounts to both Companies House and HMRC, as each authority operates under separate requirements.
2. **Software Mandate**: The government's joint Company Accounts and Tax Online (CATO) postal service closed on 31 March 2026, meaning all files must now go through commercial iXBRL software.
3. **Public P&L Changes**: Beginning in April 2028, small entities will have to register their full Profit and Loss (P&L) accounts under new transparency laws.
4. **Strict Deadlines**: Statutory accounts must reach Companies House within nine months from your company's Accounting Reference Date (ARD).

## What accounts and documents must a small UK limited company file?

A small UK limited company must file annual statutory accounts with Companies House and a full corporation tax return with HMRC. While both filings originate from the same set of books, the information disclosed to each authority is managed differently to balance tax accountability with commercial privacy.

At Companies House, small businesses are currently permitted to submit simplified, "filleted" accounts. Filing filleted accounts means you do not have to put your Profit and Loss statement or directors' report on the public register. However, you must still file a balance sheet showing the company's financial position, signed by a director, alongside specific notes details.

For HMRC, you must submit a **CT600 Corporation Tax Return** alongside your full statutory accounts, which must include the Profit and Loss statement and detailed tax computations. Additionally, you must complete an annual **Confirmation Statement (CS01)** for Companies House to verify non-financial corporate details like your registered office address and shareholder structure.

### Who qualifies as a small company and micro-entity in 2025 and 2026?

To qualify for simplified reporting, a company must meet specific size thresholds set by UK law. For accounting periods beginning on or after 6 April 2025, your company must meet at least two of the three criteria in its respective classification tier during the financial year.

| Company Classification | Maximum Annual Turnover | Maximum Balance Sheet Total | Average Number of Employees |
| --- | --- | --- | --- |
| **Micro-entity** | No more than £632,000 | No more than £316,000 | Up to 10 employees |
| **Small Company** | No more than £15 million | No more than £7.5 million | Up to 50 employees |

## What are the deadlines for UK company filing?

Your company's filing deadlines are determined directly by its Accounting Reference Date (ARD), which marks the final day of your financial year. First-year companies are granted a longer period to complete their initial setup, while established businesses operate on standard annual timelines.

| Obligation Type | Deadline for Established Companies | Deadline for First-Year Companies | Filed Registry |
| --- | --- | --- | --- |
| **Statutory Accounts** | 9 months after the ARD | 21 months from the date of incorporation | Companies House |
| **Corporation Tax Payment** | 9 months and 1 day after the ARD | 9 months and 1 day after the accounting period | HMRC |
| **CT600 Tax Return** | 12 months after the ARD | 12 months from the end of the accounting period | HMRC |
| **Confirmation Statement** | Within 14 days of the annual review date | Within 14 days of the incorporation anniversary | Companies House |

## What are the new rules for filing with iXBRL software from April 2026?

From 1 April 2026, companies must file their tax returns and accounts using commercial, third-party software as the free government CATO portal has closed. Under the new digital regulations, manual data entry and paper-based accounts are no longer permitted for standard submissions.

This policy ensures that all tax and company accounts are submitted in **iXBRL format** (Inline Extensible Business Reporting Language). This machine-readable format allows regulatory systems to instantly read and process your financial statements. Small business directors must secure commercial accounting software or hire a professional accountant with compatible software to process their financial submissions.

## When will public Profit and Loss filing become mandatory for small companies?

Under the **Economic Crime and Corporate Transparency Act 2023**, small companies will be required to file a Profit and Loss account commencing in April 2028. This upcoming statutory reform removes the option to file filleted accounts, ending the practice of withholding basic P&L figures from regulatory filings.

Crucially, the legislation includes provisions allowing eligible small businesses to opt out of having their filed Profit and Loss sheet displayed publicly. While Companies House, HMRC, and law enforcement agencies will have full access to these documents, the figures will not be shared openly on the public register. This measure is designed to combat white-collar crime while offering protection to sensitive small businesses.

## What are the late filing penalties for Companies House and HMRC?

Late filing penalties in the UK are progressive and automatically issued the day after a deadline is missed. Companies House levies immediate fines for late accounts, while HMRC processes distinct financial penalties for both overdue tax returns and unpaid liabilities.

| Overdue Duration | Companies House Penalty Amount | HMRC CT600 Penalty Amount |
| --- | --- | --- |
| **1 day late** | £150 | £100 |
| **Up to 3 months late** | £375 | £100 (plus potential interest on unpaid tax) |
| **3 to 6 months late** | £750 | £200 total fixed penalty |
| **Over 6 months late** | £1,500 | £200 plus 10% of any unpaid tax liability |
| **12 months late** | £1,500 | £200 plus an additional 10% of unpaid tax |

Please note that if your company files its annual accounts late with Companies House two years in a row, all listed penalties are automatically doubled. If you miss your payment date, HMRC also charges daily interest on any outstanding corporation tax from the first day of default.

### What is the difference between my HMRC tax return and Companies House accounts?

Companies House accounts are public financial statements displaying your annual balance sheet to show your business's financial health, whereas your HMRC tax return consists of a private CT600 form detailing corporate tax calculations and full internal accounts.

### Can small companies still file filleted or abridged accounts?

Yes, small companies and micro-entities can currently submit filleted or abridged accounts to protect their P&L from public view. However, this option will be abolished when the Economic Crime and Corporate Transparency Act 2023 transitions to its final phase in April 2028.

### How can I file my small company accounts now that the government CATO tool is closed?

With the closure of the joint Company Accounts and Tax Online service on 31 March 2026, you must purchase accredited commercial accounting software or employ a qualified accountant who can generate and send your iXBRL files directly down the digital pipeline.

### What happens if my company files its accounts late two years in a row?

If you file your accounts late with Companies House in two consecutive financial years, all late filing penalties are doubled automatically. For example, a filing received up to one month late will generate a £300 penalty instead of the standard £150 fine.