Setting up a Government Gateway account to file Corporation Tax

Last updated: 12 October 2026

Short version. Gateway User ID and Gateway Password are the Government Gateway sign-in details for the HMRC business tax account that has Corporation Tax added and activated for this company. To file your Corporation Tax return (the CT600) with HMRC, you need that account. You add Corporation Tax to it with the company's 10-digit UTR, then activate it with a code HMRC posts to the registered office within 10 days. Start well before your filing deadline.

Go to the steps and entry details

On this page

HMRC sign-in detailsEvery CT600 in this filingWhere you see it: Filing credentials › HMRC Government Gateway

Before entering figures, the filing setup questions can set the existing destination and CT600 route for an ordinary limited company. They keep the full accounts dates beside the CT600 dates. You can also continue with the controls below without opening the questions.

What this guide covers

Gateway User ID and Gateway Password are the Government Gateway sign-in details for the HMRC business tax account that has Corporation Tax added and activated for this company.

HMRC online services offers Government Gateway sign in with a user ID of up to 12 characters and a password. The filing wizard asks for that user ID and password. GOV.UK: which sign in details to use
The account must list Corporation Tax for the company you are filing, and that service must be activated. A correct password on an account without it is still refused.
The user ID, the password and the company's UTR must all belong to the same account. HMRC refuses the submission if any one of them does not match.
These details are for HMRC only. Companies House filings use the company authentication code instead. Companies House authentication code

Is this the right guide for you?

Use it if all of these are true

You are sending a CT600 to HMRC with us.
You need the Government Gateway user ID and password to enter, or you have not yet added Corporation Tax for this company.
You have, or can find, the company's 10-digit Corporation Tax UTR.

Do not use it if

HMRC has already refused your details with an Authentication Failure.Use instead: HMRC rejected my sign-in details but they are correct
You only need to find the company UTR.Use instead: Where to find your company UTR
You are filing accounts to Companies House only.Use instead: Companies House authentication code

Why you need it

When you approve the filing and select Submit, the platform sends your CT600 directly to HMRC using your own Government Gateway user ID and password. Support staff do not submit it manually. HMRC checks that those details sign in to an account that has Corporation Tax added and activated for the UTR you entered. If you have never filed this company's Corporation Tax online before, set that up first. We ask for the user ID and password only in the final filing dialog, and its user ID and password fields start empty every time you open it.

Common mistake: signing in with the wrong account

Many people have more than one Government Gateway user ID: one for their personal tax, and one or more for businesses. Each can be correct on its own. If the user ID you enter belongs to a personal account, or to another company's account, HMRC refuses the submission with the same Authentication Failure it uses for a wrong password. Before you file, sign in with the user ID you plan to use and check that Corporation Tax is listed with this company's UTR.

More help: HMRC rejected my sign-in details but they are correct

Worked example

Company: Hornbeam Example Ltd
Accounts period: 1 March 2025 to 31 May 2026 (15 months, so two CT600s)
Corporation Tax on the account: Added with the company’s UTR, then activated with the code HMRC posted to the registered office
What the director enters when filing: The company’s UTR, the user ID of that business tax account and its password, once for both CT600s

The company and all figures on this page are fictional.

Before you start

Company registration number: The number Companies House gave the company. HMRC asks for it when you add Corporation Tax.
Date the company started to do business: HMRC asks for it when you add Corporation Tax. The first accounting period starts on that date.
Date the first accounts are made up to: HMRC asks for it when you add Corporation Tax.
Company UTR: Ten digits, on letters from HMRC. Where to find your UTR
Registered office address: HMRC posts the activation code there, so check Companies House has the current address.

The company and all figures on this page are fictional.

More help: GOV.UK: what you’ll need to add Corporation Tax

Add Corporation Tax to your business tax account

Go to HMRC online services: sign in or set up an account and sign in to your business tax account with your Government Gateway user ID and password. If you do not have a user ID, select Create new sign in details and follow the steps.
Select Services you can add in the left hand menu.
Find the Corporation Tax service and select Enrol for service.
Enter the details HMRC asks for, including the company's registration number and its 10-digit UTR.

These steps come from HMRC's guide. HMRC's own screens can change, so follow what they show. GOV.UK: how to add Corporation Tax services

The activation code

HMRC then posts a Corporation Tax activation code and instructions to the company's registered office address. GOV.UK says it arrives within 10 days, or 21 days if you live abroad. Follow the instructions in that letter to activate the Corporation Tax service. If the code does not arrive, or it has expired, you can request a new one.

Once Corporation Tax is activated, you can file the CT600 with us using that user ID and password. The activation code is used once with HMRC. Never enter it in the Gateway Password field.

More help: GOV.UK: what happens next

Enter the details when you file

Review & file
Subscribe
Click Unlock Filing and complete payment, if you have not already
Continue
Click Continue to submission
Filing credentials
Filing targets
HMRC tickedOn a new filing, already ticked when you chose an HMRC option under What are you filing?.
Corporation Tax UTR
Your company’s 10-digit UTRIt may already be filled in from your company details. Check it. Where to find it
Gateway User ID
The user ID of the business tax account that lists Corporation Tax for this companyUp to 12 characters. Spaces you paste are removed automatically.
Gateway Password
The password for that same user IDUsed exactly as you type it, including any spaces.
Select the director submitting this return
The director submitting the returnAn unincorporated club or charity sees Signatory submitting this return instead.
Accounts approval date
The date the board approved the accountsNot shown for File only the remaining CT600, clubs or charities. Accounts approval date
Declaration
Tick it
Click Submit to HMRC, or Submit to HMRC & Companies House if Companies House is ticked too. If the button stays grey, the line above it starting Still needed before you can submit: lists what is missing.
More help: If HMRC rejects your sign-in details
After you submit
The filing page lists each CT600 under Gateway submissions as HMRC Government Gateway · CT600. It shows Accepted once HMRC confirms it. HMRC usually replies within a few minutes, but it can take longer. If HMRC refuses the details, the page reads Gateway details and UTR not accepted and the return shows Rejected.
More help: Filing statuses explained · Fix an Authentication Failure

Two CT600s for a long period

When your accounts period ends more than 12 months after it starts, even by one day, HMRC needs two CT600s. You enter the UTR, user ID and password once. We send both returns with those same details, one after the other. How the dates are split

The filing page shows each return on its own row, numbered like Return 1 of 2, each with its own status.
The second return is still sent if HMRC refuses the first. Because both use the same details, an Authentication Failure usually affects both.
Re-submit to HMRC → sends both CT600s of the period again, including any return HMRC has already accepted. What a repeat of an accepted return means
With File only the remaining CT600, only the second CT600 is sent, so the filing page shows one return. File only the remaining CT600

Sample outcome

Two CT600s sentFor Hornbeam Example Ltd, both returns go to HMRC with the same Government Gateway details.

One row per returnEach return shows its own status under Gateway submissions.Statuses explained

Companies House separateAccounts use the company authentication code, not these details.Authentication code

More than one company

If you are a director of more than one company, check which Government Gateway user ID lists Corporation Tax for the company you are filing for now. The user ID, password and UTR you enter must all belong to that one account. Using the user ID you set up for another company is the most common cause of an Authentication Failure for directors of several companies.

Finding your UTR

The UTR is a 10-digit number HMRC issues for the company's Corporation Tax. You find it on letters from HMRC, such as a notice to file a Company Tax Return or a payment reminder, and on a previous Company Tax Return. It is not your personal UTR, and it is not the company registration number. GOV.UK says that if no UTR has arrived 15 working days after you registered the company, you can request it online.

See where to find or request your company UTR if the letter is missing or you are not sure which number to use.

Do this before your deadline

After HMRC activation: return to the final filing dialog and enter the company's UTR, Government Gateway user ID and password. The HMRC set-up steps above are separate from preparing a draft preview.

Because the activation code comes by post, do not leave this until the day your return is due. Add Corporation Tax, wait for the code, activate it, and check that you can sign in and see Corporation Tax for the company. Then come to us to file. Your Review & file page shows your filing and payment deadlines.

If you cannot sign in. You can recover or reset a lost user ID or password. HMRC tells you how when you try to sign in. Too many wrong attempts lock the account for 2 hours. GOV.UK: help with signing in

Already set up but HMRC keeps refusing your details. HMRC returns the same error whether the password is wrong, the account is not enrolled, the enrolment was never activated, or the UTR belongs to another company. See HMRC rejected my sign-in details but they are correct to work out which one it is.

Not the right guide?

Open the guide for the detail you are stuck on.

HMRC rejected my sign-in detailsAuthentication Failure after you submitted.Where to find your company UTRThe 10-digit Corporation Tax reference.Companies House authentication codeThe 6-character code for filing accounts.

Looking for a different field or step? See all filing wizard guides →

Official sources

Whether this route matches your filings is for you to decide, yourself or with your accountant.

Example companies and figures are fictional. Field names match the filing wizard as of 12 October 2026.