The Software-Only Accounts Filing Mandate: How ECCTA Will Quietly End Free WebFiling at Companies House

Of all the changes the Economic Crime and Corporate Transparency Act 2023 (ECCTA) has set in motion, the one most likely to land in the post of an ordinary company director is also the one Companies House has talked about least: the end of free, browser-based accounts filing.

WebFiling, the registrar's online portal, has been the default route for small and micro-entity accounts for roughly sixteen years. It is free, javascript-light and forgiving — a director can sign in with an authentication code, key in turnover and creditors, and tick the small-company exemption boxes without ever touching an iXBRL tag or an API key. ECCTA hands Companies House the statutory hook to retire it, and the transition is now well into its quieter middle phase.

This piece walks through what the software-only mandate actually requires, who pays for it, and why the policy choice is more consequential than the press notices suggest.

The statutory hook

Section 56 of ECCTA inserts a power into the Companies Act 2006 allowing the registrar to require that accounts (and a defined list of associated documents) be delivered "by electronic means" and "using a software product" specified by Companies House. The wording is broad on purpose: it lets the registrar phase out non-software routes — paper, joint filing with HMRC, and WebFiling — without further primary legislation.

The registrar's own published transition plan, refreshed during 2025, set out a three-step path:

1. Phase one — full P&L disclosure for small and micro entities, removing filleted accounts as a filing option (covered in our earlier piece on the end of filleted accounts).
2. Phase two — withdrawal of the joint accounts filing service shared with HMRC, ending the single submission route that around 90,000 micro-entity directors used each year.
3. Phase three — closure of WebFiling for accounts, leaving software-API filing as the only route for every company on the register.

Phases one and two have largely landed. Phase three is the one most directors have not yet noticed.

What the mandate actually requires

"Filing by software" is a precise technical specification, not a loose policy direction. To meet it, a submission must:

• Be in iXBRL (Inline eXtensible Business Reporting Language) format, with the company's accounts tagged against the FRC's taxonomy suite — currently the FRS 101, FRS 102 and FRS 105 schemas.
• Be submitted via the Companies House Accounts Filing API using a presenter ID and authentication code, or via a software product authenticated on the user's behalf.
• Pass server-side validation against the schema in real time. Submissions that fail validation never reach the public register; there is no informal triage as there was on paper.
• Carry an audit trail captured by the software vendor, including timestamp, presenter, and accepted-by-registrar markers.

The gap between this and WebFiling is structural. WebFiling effectively wraps a HTML form around a thin XBRL generator that builds the file behind the scenes; software-only filing exposes the underlying machinery and pushes responsibility for tag completeness and arithmetic integrity onto the filer's tooling.

Who is actually affected

The Companies House register holds roughly 5.4 million companies, of which around 4.4 million are active. Strip out dormants, audit-exempt micro-entities and small companies, and the picture looks like this:

In other words, around 4.4 million annual filings — comfortably over 90 per cent of all accounts hitting the register — are made by entities currently relying on free or low-cost routes that will not survive the transition.

The software market that has formed around the mandate

A Companies House-approved software vendor list has existed since the API was opened in 2011, but it sat largely dormant until ECCTA gave it commercial reason to grow. The current list contains around forty products, ranging from full ERP suites that happen to include CH integration through to single-purpose filers built specifically for small companies. The pricing tiers below give a feel for what the WebFiling alternative now costs:

For a director who has been filing dormant company accounts in three minutes for free, the new floor is roughly £40 per year per company — or the equivalent advisory fee from an accountant who absorbs the software cost. That is a real shift in incidence, even if the numbers look modest at the per-company level.

The data-quality argument

Companies House's stated justification for the mandate is data quality, and it is the strongest part of the policy case. Three pieces of evidence run in its favour:

• Roughly 9 per cent of accounts filed on paper in 2023-24 were rejected at first attempt, against around 0.8 per cent of software-filed accounts.
• The registrar's own quality assurance sampling found that 11 per cent of WebFiled micro-entity accounts contained at least one arithmetical or balance-sheet inconsistency, against around 2 per cent for accounts filed via established practice software.
• iXBRL-tagged accounts are machine-readable end to end, which is what allows the registrar — and downstream consumers such as credit reference agencies — to compute multi-year trends without manual rekeying.

The data-integrity story sits alongside, and partly justifies, the new full-P&L disclosure regime, the registrar's enhanced enforcement powers, and the broader corporate transparency thrust of ECCTA. Without iXBRL on every submission, much of the new register simply does not work as a queryable dataset.

The DIY-director casualty

There is, however, a quieter cost. Roughly 1.6 million UK companies file their own accounts without a regular accountant — a population skewed towards micro-entities, dormants, single-shareholder service companies and family investment vehicles. WebFiling was, for this group, free in cash terms and almost free in cognitive terms. Software-only filing changes both.

The registrar's transition impact assessment estimated a £21 million annual aggregate cost for the directly-affected population once the WebFiling switch-off completes. That is a modest figure in macro terms but a meaningful one if you are the sole director of a dormant non-trading company holding a single share, where the regulatory burden has just become the dominant operating expense.

The likely behavioural response is concentration. Inform Direct, Easy Digital Filing and Xero have each reported step-changes in micro-entity subscriptions during 2025, suggesting that the long tail of self-filers is migrating into a handful of low-cost software platforms rather than disappearing back to paper or to a full-service accountant.

The alignment with HMRC

The other reason the mandate has progressed quickly is alignment. HMRC has required iXBRL-tagged accounts as part of the CT600 corporation tax return since 2011, meaning roughly 2 million UK companies already produce a software-generated, tagged accounts file every year — they just deliver a second, untagged WebFile copy to Companies House to satisfy the registrar separately.

The software-only mandate closes that duplication. Once it is fully phased in, the same iXBRL file will satisfy both the registrar and HMRC, and the joint filing service can be retired without any net loss of capacity. That is, in regulatory terms, an elegant outcome — and one of the few ECCTA workstreams that genuinely reduces filer burden in aggregate, even as it raises the cost floor for the smallest companies.

What companies should be doing now

For most directors with an accountant, the transition is invisible: the practice handles the software choice and absorbs the licence cost into the fee. For the self-filing tail, three practical points apply.

1. Confirm whether the current filing route — WebFiling, joint accounts service, or paper — is going to survive the next filing window. The registrar publishes withdrawal timetables by document type.
2. If migrating to software, choose a product authorised against the relevant FRS taxonomy (FRS 105 for micro-entities, FRS 102 Section 1A for small companies). Authorisation is listed on the registrar's published software list, not in vendor marketing.
3. Treat the first software-filed set of accounts as a dry run. Validation rejections are now binary — they do not appear on the register at all — and a rejected submission close to the s.442 filing deadline triggers automatic late-filing penalties from the unmoved £150 floor upwards.

The bigger picture

ECCTA's set pieces — identity verification, the appropriate address rule, suppression of personal data, the new fraud offence — have absorbed most of the editorial attention. The software-only filing mandate is quieter, more technical, and more easily missed. It is also the change most likely to alter the experience of being a UK company director.

For sixteen years, filing annual accounts at Companies House has been free at the point of submission for the entities that make up the bulk of the register. ECCTA does not change the statutory duty to file under s.441 — but it does change what "filing" practically means, and who supplies the tooling that makes it possible. The free filing layer is not being abolished by accident. It is being closed down because the data behind it is, by 2026 standards, no longer fit for the purpose the register is being asked to serve.