Companies House Authentication Code: Where to Find It
Lost your Companies House authentication code? Learn what it is, where to find yours, how to request a replacement, how long it takes, and how it works for an SPV.
You expected to log in, click a button, and file your confirmation statement in five minutes. Instead you are staring at a request for your Companies House authentication code, a six-character string you have never consciously seen, let alone saved. The deadline is days away, the online service will not move without it, and nothing in your records seems to match. This is one of the most common administrative hold-ups for company directors, and it is entirely solvable once you understand how the code works.
In this article you will learn exactly what a Companies House authentication code is, where to find yours, how to request a replacement if it has vanished, how long each route takes, how the rules work for an SPV, and how to keep the code safe so you never get stuck at a deadline again.
Key Takeaways
- A Companies House authentication code is a six-character alphanumeric code that acts as your company's electronic signature for online filings. It belongs to the company, not to you as an individual.
- The original code is posted to the company's registered office shortly after incorporation. It is not displayed in full anywhere online afterwards.
- If you have lost the code, you request a reminder through WebFiling and Companies House posts it to the registered office, which can take up to 10 working days.
- You cannot file a confirmation statement, annual accounts, or most other documents online without this code, so retrieve it well before any deadline.
- The authentication code is separate from both your GOV.UK One Login sign-in and your personal identity verification code. These three things are commonly confused.
- You can change the code to one you choose through WebFiling, which is worth doing if it may have been shared too widely.
What is a company authentication code?
A company authentication code is a six-character alphanumeric code issued by Companies House that authorises online filings for a specific company. It works as the digital equivalent of a company officer's signature, confirming that whoever submits a document online is permitted to do so. Without it, the online filing service will not accept anything.
The code is tied to the company registration number, not to any individual. A company has a single active authentication code at any given time, shared by everyone authorised to file for that company. If three directors all need to file, they all use the same code. This keeps filing authority with the company rather than scattering it across people, but it also means the code needs careful handling, because anyone who holds it can file on the company's behalf.
The code is made up of letters and numbers, and should be recorded exactly as issued. It is separate from two other credentials that people routinely confuse it with. Your GOV.UK One Login gets you into the filing service. Your personal identity verification code confirms who you are as a director. The authentication code authorises the actual submission for a particular company. All three are needed at different points, and losing track of which is which is a frequent source of delay.
Where do I find my Companies House authentication code?
Your authentication code was posted to the company's registered office shortly after incorporation, on a letter from Companies House, and it is not shown in full anywhere online after that. There is no screen you can log into that simply displays the existing code. This is a deliberate security measure and the single biggest reason directors struggle to locate it.
If you formed the company through a formation agent or an accountant, they are usually the fastest route, because the code often sits in their records or client portal rather than reaching you directly. If you formed the company yourself directly with Companies House, the original letter will have gone to the registered office, so search any correspondence from around the incorporation date.
Direct answer: How do I get my Companies House authentication code? If you already have one, check your formation agent, accountant, company records, and the original incorporation letter. If you cannot find it, request a replacement through the Companies House WebFiling service, which posts it to the registered office.
Where to look first, in order of speed:
- Your formation agent or accountant, if either handled the incorporation.
- Their online client portal or company secretarial software.
- The original incorporation letter posted to the registered office, which you may have filed alongside your certificate of incorporation.
- Your own filing records or document folder for the company.
- Any earlier internal note where you saved the code yourself.
How do I request a new company authentication code?
If you cannot find the original code, request a reminder or replacement through Companies House WebFiling, and it will be posted to your company's registered office address. WebFiling currently uses GOV.UK One Login to sign in, so you will need one of those accounts (or to create one) before you can make the request. The code cannot be emailed or read out over the phone, because posting to the official registered address is how Companies House confirms you are entitled to it.
To request it, sign in to WebFiling with your GOV.UK One Login, select the option to request an authentication code, and enter the company registration number. The system then triggers a letter to the registered office.
There is an important catch. The reminder goes to the registered office on record, so if that address is out of date or you no longer have access to it, you have a problem, because updating the registered office online itself needs the code. The workaround is to change the registered office using the paper form, which does not require the code, and then request the code once post reaches the new address.
How long does it take to get a Companies House authentication code?
A replacement authentication code is posted to the registered office and can take up to 10 working days to arrive, although it often comes sooner, within around five working days. There is no express, same-day, or email option, so you should treat the postal timescale as fixed and plan around it.
The original code issued at incorporation follows the same postal route to the registered office, so allow a similar window when a company is newly formed. This matters for planning. If a confirmation statement or set of accounts is due within a week or two and you have lost the code, the postal delay can push you past the deadline. Requesting the code at the first sign you cannot find it, rather than the night before filing, is the simplest way to avoid penalties.
What do I need the authentication code for?
You need the authentication code for virtually every online filing a company makes, including the confirmation statement, annual accounts, changes to directors, changes to the registered office, and share allotments. If you intend to manage the company online rather than on paper, you will use the code throughout the company's life.
The table below sets out the most common filings and whether the code is required.
Do I Need the Code for That? Common Filings at a Glance
| Filing or action | Authentication code needed for online filing? | Typical deadline |
|---|---|---|
| Confirmation statement | Yes | Within 14 days of the review date each year |
| Annual accounts | Yes | 9 months after the accounting period end (first accounts: 21 months from incorporation) |
| Change of registered office | Yes | File promptly after the change |
| Appoint or remove a director | Yes | Within 14 days of the change |
| Change of company name | Yes | File promptly after the resolution |
| Allotment of shares | Yes | Within one month of allotment |
| Viewing public company data | No | Not applicable |
The pattern is simple. Reading information on the public register is free and open to anyone, but changing the register requires the code. If you only want to look at your company's details, you do not need it. The moment you want to submit anything, you do.
What is the authentication code for an SPV?
The authentication code for an SPV is the same Companies House authentication code used by any other UK limited company, because Companies House does not treat a special purpose vehicle as a separate category. A property SPV, a buy-to-let SPV, or any landlord SPV is incorporated as an ordinary limited company, so the six-character code is posted to its registered office at incorporation and governs all that company's online filings.
The practical wrinkle for SPVs is volume. Property investors frequently form a separate SPV for each property or each lender, often in bulk through an accountant or formation agent. The authentication codes for landlord SPVs therefore tend to sit with that adviser rather than with the investor, and a landlord holding five buy-to-let SPVs can end up with five separate codes and no clear record of which belongs to which company. Because confirmation statement dates for different SPVs often fall close together, a lost code for one company can quickly become a cluster of near-simultaneous filing problems. The fix is to keep a secure record linking each company number to its code and confirmation date, so filings across a property SPV portfolio stay on schedule.
A real scenario: a property SPV and a looming deadline
A landlord incorporated a property SPV in March 2024 through a formation agent to hold a buy-to-let flat. The code letter went to the registered office, which was the accountant's address, and the landlord never saw it. Twelve months later, in March 2025, the confirmation statement fell due, with a 14-day window from the review date.
The landlord tried to file, hit the request for the authentication code, and had no record of it. They asked the accountant on day three of the window. The accountant retrieved the code from their portal the same day and the landlord filed on day four, comfortably inside the deadline. Had the accountant not held it, a fresh code would have had to be posted to the registered office, taking up to 10 working days and almost certainly blowing the window. The lesson is that knowing exactly where your code sits, before you need it, is what keeps a tight deadline safe.
How do I work out my filing deadline so the code arrives in time?
Work backwards from the filing deadline, subtract the time a replacement code takes to arrive, and that tells you the latest safe date to request it. Because a posted replacement can take up to two weeks in practice, trigger the request with a comfortable buffer rather than cutting it fine.
Here is a worked example for a confirmation statement.
- Identify the review date. Say the review date is 15 June 2026.
- Add the 14-day filing window. The statement must be filed by 29 June 2026.
- Subtract the replacement code delivery time. Allowing 10 working days, which across weekends is around 14 calendar days, takes you back to roughly 15 June.
- Add a safety buffer for any forwarding step and postal variation. Subtract a further few days, landing on about 10 June.
- Conclusion. If you have not confirmed you hold the code by 10 June, request a replacement that day at the latest. Leave it beyond that point and the code risks arriving after the 29 June deadline, triggering a late filing.
The same logic applies to annual accounts, where the deadline is normally nine months after the accounting period ends. The principle never changes: find the deadline, deduct realistic postal time, and act before that date.
How do I keep my authentication code secure?
Treat the authentication code like a password, because functionally it is one, and store it somewhere you control and can retrieve quickly. A reputable password manager is the strongest option, keeping the code encrypted, searchable, and labelled with the company it belongs to. Avoid leaving it in a plain email that can be deleted or in an unsecured spreadsheet that anyone can open.
Because the code is shared across everyone who files for the company, limit who holds it to people who genuinely need filing authority. If you want to replace a code that may have been shared too widely, you can set a new one yourself through WebFiling by signing in and choosing a new six-character code, rather than waiting for a posted replacement. If you believe the code has been misused, contact Companies House. Keep a secure record of which code belongs to which company number, which is essential once you manage more than one. A short, secure, well-labelled record removes almost every version of the problem that sends directors scrambling before a deadline.
