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CT600
Hello, I cannot submit the TT generated CT600. I am told we need to register with HMRC to do this. I cannot see how to do this. We have been completing CT600 forms on line for years (were we not registered?). We have been doing MTD VAT for years. The HMRC website does not offer a portal to register for Corp Tax. Do you know how I should do this?
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MTD VAT also uses a separate connection (OAuth via Making Tax Digital), so having MTD VAT set up doesn't carry over to CT600 filing.
**First, check if Corporation Tax is already on your Gateway:**
1. Log in at gov.uk/log-in-register-hmrc-online-services
2. Look for **Corporation Tax** in the list of services on your home screen
If Corporation Tax is listed, enrolment is already complete — use that same Gateway ID and password in TinyTax at the submission step and you're good to go.
**If Corporation Tax isn't listed, you'll need to enrol:**
1. Make sure you're logged in to an **Organisation** Gateway account (not an Individual account — Corporation Tax can only be added to an Organisation account)
2. Select **Add a tax, duty or scheme**
3. Choose **Corporation Tax**
4. Enter your **Company UTR** (10-digit number from HMRC's 'Notice to deliver a Company Tax Return' letter) and your Companies House registration number
After submitting the enrolment, HMRC may post a **CT Activation Code** to your company's registered address. Once it arrives (normally 7–10 working days), log back in and enter it to complete enrolment. After that, Corporation Tax will appear in your services and TinyTax can connect.
If your current Gateway only shows Self Assessment (not Corporation Tax), you're likely on an Individual account. You'll need to create a separate Organisation account — go to gov.uk/log-in-register-hmrc-online-services, select 'Create sign in details', and choose Organisation when asked.
Once Corporation Tax shows as active, enter your Gateway User ID and password in TinyTax at the submission step.
P.S. I am impressed by the simplicity and good value using Tiny Tax.
Your Companies House accounts are accepted — that part is complete.
Your CT600 to HMRC is not showing as submitted through TinyTax. On your dashboard, the CT600 column shows a green tick when HMRC accepts the return — at the moment it is showing as not yet filed.
Two possibilities:
If you enrolled your HMRC Gateway credentials and filed the CT600 directly via HMRC's own portal (the route you were working on earlier), it will not appear in TinyTax — but you can verify it by logging into your HMRC business tax account and checking under Corporation Tax.
If the CT600 still needs to be filed, you can do this through TinyTax: go to your dashboard, find the Ferguson Scientific row, click File and choose CT600.
The two ticks you are seeing may both relate to the Companies House accounts. On the TinyTax dashboard, CT600 and Accounts are shown in separate columns — both need to show a green tick for the full filing to be complete.
Sorry to be so useless.
What you need is your company's own 12-digit Organisation Government Gateway ID and password. Since you have been filing CT600s directly on HMRC's website for years, you almost certainly already have one — HMRC's own CT600 portal closed on 31 March 2026, which is why you now need to file through software like TinyTax instead.
Here is what to do:
1. Log in at https://www.gov.uk/log-in-register-hmrc-online-services with your existing Organisation Gateway ID (the 12-digit number) and password
2. Check whether Corporation Tax appears in your list of services — if it does, you are fully enrolled and can enter those same credentials in TinyTax to submit your return
3. If Corporation Tax is not listed, select Add a tax, duty or scheme → Corporation Tax. You will need your company UTR. HMRC will then post a one-time activation code to your registered address (usually 7–10 working days) — once you enter that, you are ready to file
One thing to note: your MTD VAT enrolment does not automatically mean Corporation Tax is enrolled — they are separate services on your Gateway.
Full step-by-step guide: https://tinytax.co.uk/support/government-gateway-issues