Companies House Authentication Code: What It Is and How to Get It

A Companies House authentication code is easy to overlook until the moment it is needed. A director may be trying to file a confirmation statement, submit annual accounts, update the registered office, appoint a new officer or authorise an accountant to deal with Companies House filings. Then the process stops because the company authentication code is missing, not working, or still sitting in a letter sent to an old registered office.

That small code carries more practical weight than many company owners realise. It is not the same as a Companies House login. It is not the same as a director’s personal identity verification code. It is not issued by HMRC. It is the company-level electronic authority that allows certain filings to be made online for a UK company.

This guide explains what a Companies House authentication code is, what it is used for, how to get it, where to find it, what the format looks like, what to do if it is lost, and why it should be treated as a controlled company record rather than a casual admin detail.

What is a Companies House authentication code?

A Companies House authentication code is a security code used to file company information electronically with Companies House. It acts as the online equivalent of a company officer’s signature for many Companies House filings.

In practical terms, the authentication code for Companies House confirms that the person submitting certain information has authority to act for the company. Without it, a company or its adviser may be unable to complete key online filings through Companies House WebFiling or related online filing routes.

The code belongs to the company, not to an individual director, shareholder, accountant or employee. This distinction matters. If a director leaves, the company’s authentication code does not automatically become invalid simply because that person is no longer involved. Equally, a new director does not receive a separate code purely because they have been appointed.

The phrase “company’s authentication code” is often used informally, but the principle is the same: it is the company authentication code used to authorise electronic filings at Companies House.

What is a Companies House authentication code used for?

The Companies House authentication code is used for online filings relating to the company’s statutory record. It is commonly needed for matters such as filing a confirmation statement, submitting certain changes to company details, and making updates that appear on the public register.

Typical uses include:

• filing a confirmation statement;
• updating registered office details;
• appointing or removing directors and company secretaries;
• changing officer details;
• filing certain annual accounts online;
• updating people with significant control information;
• authorising online activity through Companies House systems.

The exact filing route can vary depending on the type of filing, the company structure and the online system being used. Some filings may also involve software filing or adviser-led filing processes. The key point is that the Companies House company authentication code is the company-level credential that allows online submissions to be accepted as authorised.

For directors, the code is part of the wider compliance infrastructure around statutory filings. For accountants and company secretarial advisers, it is often required before they can complete Companies House filing efficiently on behalf of a client. Without it, work that appears straightforward can be delayed by several days, especially if a replacement code has to be posted.

What does a Companies House authentication code look like?

A Companies House authentication code is usually a six-character alphanumeric code. It may include letters and numbers. This is why people often search for a “Companies House 6 digit authentication code” or “6 character company authentication code”, although “six characters” is the more accurate description because the code is not necessarily made up only of digits.

A simplified example of a Companies House authentication code might look like this:

A1B2C3

That is only an illustrative example, not a real code. A genuine code should be treated as confidential and should not be shared publicly, emailed casually, stored in an unsecured spreadsheet, or passed between former and current officers without proper control.

Companies House usually sends the code by post to the company’s registered office address. This is one reason the registered office needs to be monitored properly. If the company uses an accountant’s address, formation agent address, serviced office or mail handling address, the internal process for forwarding Companies House post becomes important.

Companies House password, presenter ID and authentication code: the differences

Confusion often arises because Companies House uses several credentials and identifiers. They are connected to filing activity, but they do different jobs.

Companies House authentication code

This is the company-level code used to authorise online filings for a specific company. It belongs to the company and is linked to the company number.

Companies House WebFiling password or account login

This relates to the user account used to access online filing systems. A person may have a login, but still need the company authentication code to file for a particular company.

Presenter ID

A presenter ID is generally associated with presenters who file documents, often through certain filing channels. It should not be confused with the company authentication code.

Companies House personal code

A Companies House personal code is not the same as a company authentication code. Personal codes are linked to identity verification requirements for individuals, whereas the company authentication code is linked to online filing authority for the company. As Companies House reforms continue, this distinction is becoming more important because identity verification and company filing authority are separate concepts. Readers dealing with the newer process may also need to understand how to verify your identity for Companies House separately from managing company filing access.

A useful way to think about it is this: the personal code relates to a person; the authentication code relates to the company.

How to get a Companies House authentication code

If the company does not already have its authentication code, it can be requested from Companies House. The request is usually made online, and Companies House sends the code by post to the company’s registered office address.

The basic process is:

• go to the relevant Companies House online service;
• select the option to request an authentication code;
• enter the company number and required company details;
• confirm the request;
• wait for the code to arrive by post at the registered office.

This answers the common practical question: “How do I get my Companies House authentication code?” You request it through Companies House, but you do not usually receive it instantly online. For security reasons, it is sent to the registered office.

Companies House commonly indicates that the letter can take several days to arrive. Directors should allow enough time, particularly if the company has a confirmation statement submission or accounts deadline approaching. A last-minute request can leave the business unable to file online until the code arrives.

The code is not normally sent to a director’s home address unless that address is also the registered office. It is not sent to an accountant merely because the accountant has been appointed for tax or bookkeeping purposes. Companies House uses the registered office because it is the official address for statutory company communications.

Where to find your Companies House authentication code

If the company already has a code, the first place to check is the original Companies House authentication code letter. This letter is usually sent to the registered office after the code has been requested.

In practice, the code may be found in one of several places:

• the company formation records;
• Companies House correspondence held by the registered office provider;
• the company secretarial file;
• records held by the accountant or formation agent;
• handover documents from a previous adviser;
• secure internal compliance records maintained by the company.

For newly incorporated companies, the code is sometimes requested soon after the company formation process and filed away with incorporation documents. For older companies, it may have been requested years ago and used occasionally for filings. That gap between use is one reason directors often cannot find the Companies House authentication code when they need it.

If the company has changed accountants, moved registered office, changed directors, or used a formation agent at incorporation, there may be more than one party who has historically handled Companies House post. The practical task is not just “where can I find my Companies House authentication code?” but “who controlled Companies House correspondence at the time it was issued?”

Can you get the Companies House authentication code online?

You can request the Companies House authentication code online, but the code itself is usually sent by post to the registered office. This is an important distinction.

Some directors expect to log in and view the code immediately. That is not how the process normally works. Companies House uses postal delivery to the registered office as a control measure, because the code gives access to make statutory filings on behalf of the company.

Once received, the code can be used for Companies House online filing, including WebFiling and other supported filing routes. It should then be stored securely so the company does not need to request a replacement every time a filing is due.

How long does a Companies House authentication code take?

The waiting time depends on postal delivery and Companies House processing. It is common to allow several working days for the authentication code letter to arrive, although timings can vary.

The practical issue is not usually the request itself; it is the dependency chain. If the registered office is managed by a third party, the letter may arrive there first, then need to be scanned, forwarded or processed. If the company has recently changed its registered office, the request may go to the address currently shown on the Companies House register at the time of request.

This can cause avoidable problems close to filing deadlines. A company may think it has requested the code in time, but the letter sits unopened at a serviced office, is delayed in a forwarding queue, or goes to an address no longer actively monitored by the directors.

What to do if the authentication code is lost or forgotten

If the Companies House authentication code is lost, forgotten, not received or not working, the company can request a replacement or new authentication code through Companies House. The replacement code will normally be sent to the registered office address.

Common situations include:

• the original letter has been misplaced;
• a previous accountant or formation agent held the code;
• the company changed registered office and old post was not retained;
• a director who managed filings has left the business;
• the code was stored in an inaccessible email account or document system;
• the company has not filed online for several years and no one knows where the code is held.

Requesting a new Companies House authentication code is usually the cleanest route where control is uncertain. It avoids relying on an old code that may have been shared with people who no longer act for the company.

From a governance perspective, a lost authentication code is not just an administrative inconvenience. It can reveal a wider weakness in company record keeping. If the code cannot be located, there may also be gaps in how the company stores statutory registers, confirmation statement records, accounts filing evidence, board minutes, tax references and HMRC correspondence.

Companies House authentication code not received

If the code has been requested but not received, the first step is to check the registered office address shown on the Companies House register. The code is normally posted there, not necessarily to the trading address or director’s address.

The next step is to check whether the registered office provider, accountant, company formation agent or mail handling service has received the letter. In practice, the letter may have arrived but not yet reached the person who requested it.

If enough time has passed and the letter still cannot be traced, the company may need to request the code again. Before doing so, it is sensible to confirm that the registered office address is correct and actively monitored. Repeating the request while the underlying address problem remains unresolved can simply reproduce the same delay.

Why an authentication code may not work

A Companies House authentication code may fail for several reasons. Sometimes the issue is simple typing: a letter mistaken for a number, an old code copied incorrectly, or a space added before or after the code. At other times, the company may be trying to use a code that has been replaced.

Common causes include:

• using an old authentication code after a new one has been issued;
• entering the code against the wrong company number;
• mistaking a WebFiling password, presenter ID or personal code for the company authentication code;
• copying the code incorrectly from a scanned letter;
• attempting a filing route that requires different credentials or additional authorisation;
• using details for a company with a similar name but different company number.

If the code is not working, check the company number first. This sounds obvious, but groups with multiple companies, dormant subsidiaries or similarly named entities often experience filing confusion. The code is tied to a specific company. A code for one company will not authorise filings for another.

Can you change a Companies House authentication code?

Yes, the Companies House authentication code can be changed. A company may wish to change it if the code has been shared too widely, if advisers have changed, if a director has left in difficult circumstances, or if there is uncertainty about who has access to it.

Changing the code is often sensible after a governance transition. For example, where a company has moved from a formation agent to a long-term accountant, or where responsibility for statutory filings has moved from one internal employee to another, the code should be brought under the company’s current control.

A company should not treat the authentication code as a permanent password that can be passed around indefinitely. It is better viewed as a controlled filing credential. Access should be limited to people who genuinely need it for statutory filing purposes.

Does a Companies House authentication code expire?

A Companies House authentication code does not operate like a short-lived one-time password. It does not normally expire after a few minutes or days in the way that some security codes do. Once issued, it can continue to be used unless it is changed or replaced.

That said, the fact that it does not routinely expire is exactly why it should be protected. A code issued several years ago may still be capable of authorising filings if it has not been changed. If it has been held by former advisers, former employees or former directors, the company should consider whether it remains appropriate to rely on it. Companies House procedures may also evolve as wider reforms continue, so companies should keep current filing guidance under review.

Security is not only about whether a code is technically valid. It is also about who knows it, where it is stored, and whether access reflects the company’s current governance arrangements.

The confirmation statement problem: why the code is often discovered late

The Companies House authentication code is frequently noticed only when the annual confirmation statement is due. The company may have traded normally throughout the year, kept accounts, submitted VAT returns, run payroll and dealt with HMRC, only to find that a Companies House filing cannot be completed because the authentication code is missing.

This is a common operational mismatch. Tax compliance and Companies House compliance are related but separate. A business may be fully up to date with HMRC for VAT, PAYE or Corporation Tax and still have a Companies House filing obstacle. Conversely, a company may have filed its confirmation statement but still have tax or accounts work outstanding.

The confirmation statement is especially sensitive because it confirms key information on the public register. If the authentication code is unavailable, directors may lose valuable time while waiting for a replacement. The same issue can arise with Companies House annual accounts filing, especially where the accounts have been prepared close to the deadline and the online filing step is left until the end.

Why registered office control matters more than most directors expect

The authentication code process exposes a wider point about company administration: the registered office is not just a formal address. It is where statutory communications are sent, and it can determine whether important information reaches the right person in time.

Problems often appear where a company has used:

• a formation agent’s address at incorporation and never updated internal records;
• a serviced office with slow mail forwarding;
• a former accountant’s address;
• a director’s previous home address;
• a group company address without clear responsibility for post;
• a virtual office where Companies House letters are not prioritised.

None of these arrangements is automatically wrong. The issue is control. Someone must be responsible for receiving, reviewing and acting on Companies House correspondence. If no one owns that process, the authentication code is often the first visible symptom of a deeper filing control weakness.

Authentication code for accountants and advisers

Accountants, bookkeepers and company secretarial advisers may need the Companies House authentication code to complete filings for a company. This is normal, but it should still be handled carefully.

Giving an adviser the code does not transfer directors’ responsibilities. Directors remain responsible for ensuring that company filings are accurate and submitted on time. Advisers can support the process, prepare documents, manage filing workflows and reduce administrative errors, but the company’s statutory duties remain with the company and its officers.

A practical approach is to record which adviser has access to the code, why they need it, and where the code is stored. If the adviser relationship ends, the company should consider changing the authentication code, particularly if there has been a long period of shared access or if multiple staff at the adviser firm handled filings.

Authentication code and wider compliance records

The Companies House authentication code sits alongside a broader set of company records and compliance details. It should not be managed in isolation.

A well-controlled company will usually keep secure records of:

• company number and incorporation documents;
• registered office details;
• Companies House authentication code;
• confirmation statement filing history;
• annual accounts filing evidence;
• statutory registers and PSC records;
• HMRC references for Corporation Tax, PAYE and VAT where applicable;
• board approvals and key governance decisions;
• details of advisers authorised to file on the company’s behalf.

This matters because Companies House filings rarely exist in a vacuum. An appointment of a director may also affect payroll setup, authorisation processes, bank mandates and internal approvals. A change of registered office may affect HMRC correspondence and supplier records. Annual accounts filed at Companies House should align with the company’s accounting records and Corporation Tax position, even though Companies House and HMRC are separate bodies.

For small companies, this may feel more formal than day-to-day trading requires. But most filing failures do not begin with technical complexity. They begin with unclear ownership: no one knows who holds the code, who checks deadlines, who receives letters, or who confirms that filings have actually been accepted.

Common mistakes with Companies House authentication codes

The most common mistakes are rarely dramatic. They are small administrative gaps that become urgent at the wrong moment.

• Assuming the code is the same as a Companies House login. A user account and the company authentication code are different credentials.
• Leaving the code with a former adviser. If the company has changed accountants or formation agents, access should be reviewed.
• Requesting the code too close to a deadline. Postal delivery can create avoidable filing pressure.
• Not monitoring the registered office. The code may be sent correctly but still not reach the directors promptly.
• Sharing the code too widely. The code authorises filings and should not be treated as harmless admin data.
• Confusing personal identity codes with company authentication codes. They serve different purposes and should not be used interchangeably.
• Using the wrong company number in a group structure. Each company has its own code.

These mistakes are preventable, but only if the company treats Companies House administration as part of its normal compliance process rather than an annual interruption.

A practical workflow for directors

For a company that cannot locate its authentication code, a practical workflow is usually straightforward.

First, confirm the company number and registered office address on the Companies House register. Then check the company’s statutory records, incorporation file and any correspondence from Companies House. If an accountant, formation agent or registered office provider has previously managed filings, ask whether they hold the code or have received the authentication code letter.

If the code still cannot be found, request a new Companies House authentication code. Allow time for postal delivery and for any registered office mail forwarding process. Once received, store it securely and decide who within the company or adviser team may use it.

After that, it is sensible to review upcoming filing dates. The authentication code is often needed because a filing is due; resolving the code issue is only part of the task. The company still needs to ensure the confirmation statement, accounts or other filing is accurate and submitted within the relevant deadline.

How this fits with Companies House reforms

Companies House is becoming more active as a gatekeeper of company information. Reforms to identity verification, data quality and register integrity are changing the expectations placed on directors, PSCs and those who file information on behalf of companies.

The authentication code remains a company filing credential, but it now sits in a compliance environment where identity, authority and accuracy are receiving greater scrutiny. Directors should expect less tolerance for casual filing habits, incomplete records or uncertainty over who is authorised to submit information.

This does not mean routine filings need to become burdensome. It does mean companies should maintain cleaner internal controls. Knowing where the authentication code is, who can use it, and how it connects to the company’s statutory filing calendar is a basic part of that control.

Key takeaways for UK companies

• A Companies House authentication code is the company-level code used to authorise many online filings.
• It is usually a six-character alphanumeric code, not necessarily a six-digit number.
• The code belongs to the company, not to an individual director or accountant.
• You can request a Companies House authentication code online, but it is normally sent by post to the registered office.
• If the code is lost, forgotten or no longer controlled, the company can request a new one.
• The code should be stored securely and reviewed when directors, advisers or registered office arrangements change.
• It is different from a Companies House login, presenter ID and personal identity verification code.
• Missing or delayed access to the code can affect confirmation statements, annual accounts filings and other statutory updates.

For directors managing recurring company obligations, the code should sit within a wider annual statutory compliance process rather than being treated as a one-off filing detail.

Final perspective

The Companies House authentication code is a small credential with a large administrative role. It does not prepare accounts, resolve tax questions or decide whether company information is correct. But without it, online filing can stall at precisely the point where timing matters.

For directors, the better approach is to treat the code as part of the company’s compliance infrastructure. Keep it secure. Know who has access. Review it when advisers or officers change. Make sure the registered office is monitored. Request a replacement before a deadline becomes urgent, not after.

Handled well, the authentication code is barely noticeable. Handled poorly, it becomes a filing bottleneck, a governance concern and a reminder that statutory compliance depends as much on practical administration as it does on technical rules.