Government Gateway and Corporation Tax Enrolment

To file a CT600 through TinyTax, you need to connect your HMRC Government Gateway account. This guide explains how Government Gateway works, how to enrol for Corporation Tax, and how to fix common issues.

What Is Government Gateway?

Government Gateway is HMRC's online login system. It's separate from Companies House — they are two different systems with different credentials:

System	What it's for	Credential
Government Gateway	HMRC services (CT600, PAYE, VAT)	12-digit Gateway ID + password
Companies House	Filing accounts, company changes	6-character authentication code

TinyTax needs your Government Gateway credentials to submit your CT600 to HMRC. Your Companies House authentication code is used separately when filing accounts.

Organisation vs Individual Accounts

Government Gateway has two account types. Corporation Tax can only be added to an Organisation account.

Account type	Used for	Can enrol for CT?
Individual	Personal tax (Self Assessment)	No
Organisation	Business taxes (CT, PAYE, VAT)	Yes

⚠ If you're trying to add Corporation Tax to your personal (Individual) Gateway and it won't work, this is likely the reason. You need a separate Organisation account for your company.

How to check your account type

Log in at gov.uk/log-in-register-hmrc-online-services
Look at what services are listed — if you see "Self Assessment" but not "Corporation Tax", you're on an Individual account

How to Enrol for Corporation Tax

Step 1: Create an Organisation Gateway account (if needed)

If you only have an Individual account:

Go to gov.uk/log-in-register-hmrc-online-services
Select Create sign in details
Choose Organisation when asked what type of account
Complete the setup — you'll receive a new 12-digit Gateway ID

Step 2: Add Corporation Tax to your account

Log in to your Organisation Gateway account
Select Add a tax, duty or scheme
Choose Corporation Tax
You'll need:

- Your Company UTR (10-digit Unique Taxpayer Reference — from HMRC's "Notice to deliver a Company Tax Return" letter) - Your company registration number (from Companies House)

Step 3: Connect to TinyTax

Once Corporation Tax appears in your Gateway services:

In TinyTax, go to the submission preview page
Enter your Company UTR, Gateway ID, and Gateway password when prompted
TinyTax connects directly to HMRC to submit your return

Common Problems

"Company not listed" or "not recognised"

This usually means one of:

You're using an Individual Gateway — Corporation Tax requires an Organisation account (see above)
HMRC hasn't processed your CT registration yet — after incorporation, HMRC automatically registers your company for CT, but this can take several weeks. If your company is very new, you may need to wait
Your UTR is incorrect — double-check the 10-digit number from HMRC's letter

Stuck in a loop when trying to enrol

If HMRC keeps redirecting you back to the same page:

Make sure you're logged into an Organisation account, not Individual
Try a different browser or clear your cookies
If the problem persists, call HMRC's Corporation Tax helpline: 0300 200 3410

Agent has CT access on their Gateway

If your accountant or agent has Corporation Tax registered on their Gateway:

This doesn't necessarily prevent you from also enrolling on your own Gateway
If HMRC won't let you enrol, ask your agent to de-authorise their CT access first
Alternatively, your agent can file on your behalf using their own software

Multiple Gateway accounts

If you accidentally created multiple Gateway accounts:

Only one Organisation account should have Corporation Tax enrolled
You can call HMRC to delete unused Gateway accounts: 0300 200 3600
Make sure you know which Gateway ID has CT enrolled before deleting any

Government Gateway vs Companies House Auth Code

These are commonly confused. Here's a quick comparison:

	Government Gateway	CH Auth Code
Issued by	HMRC	Companies House
Format	12-digit ID + password	6-character code
Used for	CT600 tax returns	Company accounts filing
How to get	Create account online	Sent by post to registered office
Used in TinyTax	When submitting CT600	When submitting accounts

If you're having trouble with your Companies House authentication code, see our authentication code guide.

Common Questions

I've lost my Gateway ID — how do I find it?

Check your email for the original registration confirmation from HMRC. If you can't find it, you can recover your Gateway ID at gov.uk/log-in-register-hmrc-online-services by selecting "Problems signing in" and following the recovery steps.

Do I need a Government Gateway to file accounts with Companies House?

No. Companies House accounts use a separate authentication code, not Government Gateway. You only need Gateway for your CT600 tax return.

My company is being struck off — can I still file CT600?

Yes. You should file any outstanding CT600 returns before your company is dissolved. Your Government Gateway access remains active until HMRC closes the Corporation Tax record after dissolution.

Can I use my accountant's Gateway to file through TinyTax?

No. TinyTax requires the company's own Government Gateway credentials. If your accountant has been filing on your behalf, you'll need to set up your own Organisation Gateway account and enrol for Corporation Tax.

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