Set Up Your Government Gateway | TinyTax Support

Set Up Your Government Gateway

How to set up Government Gateway for your UK company. Step-by-step guide to creating your HMRC online account and enrolling for Corporation Tax services.

Government Gateway: Setup Guide for Companies

Government Gateway is HMRC's online portal for tax services. You'll need it to file your CT600 and manage your company's tax affairs. Here's how to set it up.

What Is Government Gateway?

Government Gateway is HMRC's secure login system. It provides access to:

  • Corporation Tax services (CT600 filing)
  • VAT services
  • PAYE for employers
  • Other HMRC services
You'll need it to: Authorise CT600 software to file on your behalf.

Before You Start

What You'll Need

  • Company registration number (8 digits)
  • Company UTR (Unique Taxpayer Reference) - 10 digits
  • Your company's registered office address
  • An email address
  • A UK mobile number (for security codes)

Don't Have a UTR?

HMRC issues your company UTR automatically when you register for Corporation Tax. This usually happens within a few weeks of incorporation.

If you haven't received it, contact HMRC: 0300 200 3410

Step 1: Create a Government Gateway Account

Go to the Portal

Visit: www.gov.uk/log-in-register-hmrc-online-services

Create Organisation Account

  1. Click "Create sign in details"
  2. Select "Organisation" (not Individual)
  3. Enter your email address
  4. Create a password
  5. Set up two-factor authentication

Save Your User ID

Important: HMRC will give you a 12-digit User ID. Save this securely—you'll need it every time you log in.

Step 2: Enrol for Corporation Tax

Add CT Service

  1. Log into Government Gateway
  2. Click "Add a tax, duty or scheme"
  3. Select "Corporation Tax"
  4. Enter your Company UTR
  5. Enter your company registration number

Verification

HMRC will send an activation code by post to your registered office address. This takes 7-10 days.

Activate the Service

  1. Log back into Government Gateway
  2. Enter the activation code
  3. Corporation Tax service is now active

Step 3: Use Your Gateway Credentials in TinyTax

How TinyTax Connects to HMRC

There is no upfront "connect" or "authorise" step for Corporation Tax in TinyTax. You don't go to a Settings page, you don't get redirected to Government Gateway, and you don't grant any standing access.

Instead, when you submit a CT600, TinyTax asks for your Gateway User ID and password in the submission form, and includes them in that single submission to HMRC. This is how HMRC's CT600 service (the Transaction Engine) is designed — it requires credentials per submission, not OAuth-style delegated access. Every CT600 software works this way.

What You'll See at Filing Time

  1. Log into TinyTax
  2. Add your company and enter your accounting period figures
  3. When you click submit, the CT600 confirmation modal appears
  4. Enter your Gateway User ID (12 digits) and password
  5. Enter your company UTR
  6. Click submit — TinyTax sends the return to HMRC and shows the response
Your Gateway credentials are not stored by default. TinyTax can offer to remember them for you on the next filing if you tick the "remember" option in the submission modal — that's the only persistence and you can clear it any time.

A Note on MTD VAT (Different Mechanism)

If you've previously connected another product to HMRC for MTD VAT, you'll have seen a "Connect to HMRC" button and an OAuth redirect to Government Gateway. MTD VAT works that way; CT600 does not. The two services use different authentication models on HMRC's side, so the setup flows look different. Don't expect the OAuth redirect for CT600 — it isn't there.

Common Issues

"Company Not Recognised"

Cause: Company number or UTR doesn't match HMRC records

Fix:

  1. Double-check both numbers
  2. Ensure no leading zeros are missing
  3. Wait if recently incorporated (HMRC needs time to update)

"Activation Code Not Received"

Cause: Postal delays or wrong address

Fix:

  1. Check your registered office address is correct at Companies House
  2. Request a new code from Government Gateway
  3. Allow 10 working days

"User ID Forgotten"

Fix:

  1. Go to Government Gateway login
  2. Click "Problems signing in"
  3. Select "I have forgotten my User ID"
  4. Follow recovery process

"Two-Factor Authentication Issues"

Fix:

  1. Ensure your mobile number is current
  2. Check for SMS from HMRC
  3. Use backup codes if set up
  4. Contact HMRC if locked out

Adding Multiple Services

Other Services You Might Need

ServiceWhat It's For
Corporation TaxCT600 filing
PAYE for employersIf you have employees
VATIf VAT registered
Construction Industry SchemeIf in construction
Each service requires separate enrolment but uses the same Government Gateway account.

Agent Access

If You Have an Accountant

Your accountant may ask for agent authorisation:

  1. Log into Government Gateway
  2. Go to "Manage account"
  3. Select "Authorise an agent"
  4. Enter the agent's reference number
  5. Confirm authorisation

What Agents Can Do

  • File returns on your behalf
  • View your tax position
  • Communicate with HMRC for you
You remain responsible for the information filed.

Security Best Practices

Protect Your Account

  • Use a strong, unique password
  • Enable two-factor authentication
  • Keep your User ID confidential
  • Log out after each session
  • Use a secure internet connection

If You Suspect Unauthorised Access

  1. Log in immediately
  2. Change your password
  3. Review recent activity
  4. Contact HMRC if concerned
  5. Remove suspicious authorisations

Frequently Asked Questions

Do I need Government Gateway if using software?

Yes. Software uses Government Gateway authentication to verify your identity and submit returns.

Can I have multiple users for my company?

Yes. You can add additional administrators in Government Gateway settings.

What if my company details change?

Update your registered office at Companies House. HMRC records update from Companies House data.

Is Government Gateway the same as Companies House WebFiling?

No. Government Gateway is for HMRC (tax). Companies House WebFiling is for Companies House (company filings). They're separate systems.

How long does setup take?

Initial account: 10 minutes. Activation code: 7-10 days. Total: About 2 weeks.

Summary Checklist

Setup Steps

  • Create Government Gateway organisation account
  • Save your 12-digit User ID
  • Enrol for Corporation Tax
  • Wait for activation code (postal)
  • Enter activation code
  • Use your Gateway User ID and password directly in the TinyTax submission form when you file

Information Needed

  • Company registration number
  • Company UTR
  • Registered office address
  • Email address
  • UK mobile number
Start this process early—the postal activation code takes time.

Related guides:

  • How to File a CT600
  • UTR Number Explained

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