SimpleReturns

Where do I find my Companies House authentication code?

Updated 15 July 2026
The short answer

Your authentication code is a short code, 6 characters long, made up of letters and numbers. Companies House posted it to your company's registered office, and it acts like your signature for anything filed online. If you can't find it, don't worry, this happens all the time and you can get a new one. Sign in to Companies House WebFiling and request it; a fresh code is posted to your registered office and can take up to 10 working days to arrive.

Official source. This guide is a plain-English summary of official GOV.UK guidance, not advice. The authoritative source is Company authentication codes for online filing on gov.uk. Always rely on that over our summary.

What is the authentication code, and why am I being asked for it?

It's a 6-character code that Companies House gives to every company. Think of it as your company's signature for the internet: when something is filed for your company online, like your yearly accounts, the code is what proves the filing was allowed.

That's why you're being asked for it now. Nothing has gone wrong, and it isn't a sign you've missed something. It's just the one piece of the puzzle that only your company holds.

One thing it is not: it's not your Government Gateway login, and it's not your company's tax reference (the UTR). Those belong to HMRC, the tax side. The authentication code belongs to Companies House, the company-records side. They're separate systems with separate codes. If it's the Gateway login you're missing, see I've lost my Government Gateway login, and if it's the tax reference, see How to find your company's UTR.

Where was my code sent in the first place?

By post, to your company's registered office address. That's the official address on the public record for your company, which may not be where you actually work.

So before you request a new one, it's worth a quick look in these places:

  • Any letters from Companies House kept from when the company was set up.
  • Wherever post for your registered office ends up, especially if the registered office is an accountant's office or a mail-forwarding address.
  • Anyone who helped set the company up or has filed for it before, like an accountant or a formation agent. If they file online for your company, they may already have the code.

If a quick look doesn't turn it up, don't spend hours hunting. Requesting a new one is simple.

How do I request a new code?

  1. Go to Companies House WebFiling on gov.uk and create an account, or sign in if you already have one.
  2. Follow the steps to request your authentication code for your company.
  3. Companies House posts the code to your company's registered office. It is post only; they won't email it or read it out over the phone.
  4. Wait for the letter. It can take up to 10 working days to arrive, and longer in busy periods.
  5. When it arrives, keep it somewhere safe, and finish whatever filing you were in the middle of.

That's the whole process. There's no form to print.

What if I've moved and can't get post at my registered office?

This is the trap that catches the most people. The code only goes to the registered office on record, so if you've moved, or the registered office is an old accountant's address you no longer use, the letter will land somewhere you can't reach.

Companies House has a route for exactly this: if you can't access your company's registered office address, they can send the authentication code to your home address instead. You do this through the Find and update company information service on gov.uk.

One thing you can't do yet: update the out-of-date registered office. Changing your company's details online is itself a filing, so it needs the very code you're waiting for. Once the new code has arrived at your home address, use it to bring the registered office up to date, and the same problem won't bite you again next year.

How long will this take?

Plan for up to 10 working days from requesting the code to the letter arriving, roughly two weeks in real terms. Companies House themselves say not to wait until your accounts are due, because delivery can take longer than usual when they're busy.

So if your filing deadline is coming up, request the code today, before you do anything else. It's the one step you can't speed up. Everything else about your filing can be prepared while you wait for the post.

How do I keep it safe once I have it?

Companies House say to treat the code with the same care as your bank card PIN. It works like a signature for your company, so anyone who has it can file things in your company's name.

  • Only share it with people you trust to file for your company.
  • If someone who shouldn't have it gets hold of it, change it. You can change or cancel the code by signing in to WebFiling.
  • If you change it, tell your accountant or anyone else who files for your company, because the old code stops working straight away.
  • Companies House will never ring you and ask for your code. If someone does, it's not Companies House.

Common questions

Is the authentication code the same as my Government Gateway login?

No. The Government Gateway login is HMRC's sign-in for the tax side of your company. The authentication code is a Companies House thing, used to approve filings on the company-records side. You can have one without the other, and losing one doesn't affect the other.

Can Companies House email me the code or tell me over the phone?

No. It comes by post, to your registered office (or your home address if you've told them you can't access the registered office). They'll never ask you for the code over the phone either, so treat any such call as a scam.

I don't think my company ever had a code. What do I do?

Request one, exactly as in the steps above. Every company can have one, and the request route is the same whether you lost the letter or never saw one.

My accounts are due in a few days and I don't have the code. Am I stuck?

Request the code right now, since the post can take up to 10 working days. Then get everything else ready while you wait, so the code is the only missing piece. If the deadline will pass before the code can possibly arrive, speak to Companies House about your options, and if things are tangled, a quick call to an accountant is honestly worth it.

My accountant has the code but we've parted ways. Should I change it?

It's sensible, yes. Change it through WebFiling so the old code stops working, then keep the new one with your company records. Just remember to give the new code to anyone who still files for you.

Stuck on this while trying to file?

This code is one of the things SimpleReturns asks for when you connect your company, and the connect step has a built-in rescue wizard for exactly this situation: it checks your sign-in first, walks you through what's missing, and gives you a before-you-start checklist so the 10-working-day letter never catches you by surprise. We use your code only to connect you and never store it permanently. It's free to start, no card needed, and filing costs £99 flat per submission.

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And if your company's situation is unusual, say the company records are in dispute, an accountant is the right call, not a website.

General guidance, not advice. This guide explains how the rules generally work for small UK limited companies. It isn't tax advice for your specific situation, if you're unsure, check with us or an accountant.