We have for many years submitted our corporation tax and ct600 to HMRC but tiny tax says HMRC credentials are not accepted. This is very confusing to us .
The error message you are seeing — "HMRC credentials are not accepted" — is HMRC returning Error 1046 (Authentication Failure). Looking at the failed submissions for WOODFINISH LIMITED, I can see the credential being sent to HMRC contains letters rather than the expected 12-digit numeric Government Gateway User ID.
The most likely cause is that the wrong credential type is being entered. TinyTax needs your **Government Gateway User ID** — the 12-character (usually all-numeric) ID that Government Gateway assigns when you register. This is different from your:
- HMRC username or email address
- Companies House authentication code
- UTR (Unique Taxpayer Reference)
**How to find your correct Gateway User ID:**
1. Go to www.gov.uk/log-in-register-hmrc-online-services
2. On the sign-in page, look for the 12-digit User ID — it is printed on your Government Gateway enrolment letter, and is also shown in your account settings once signed in
3. Enter that 12-digit ID into the "Government Gateway User ID" field in TinyTax (under HMRC credentials)
4. Make sure Corporation Tax is listed as an enrolled service on the account — if it is not, you will need to add it before you can submit
If you are still seeing Error 1046 after updating the credentials, our support guide at https://tinytax.co.uk/support/hmrc-error-1046 covers all the common causes including enrolment steps and throttle/lockout recovery.
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The most likely cause is that the wrong credential type is being entered. TinyTax needs your **Government Gateway User ID** — the 12-character (usually all-numeric) ID that Government Gateway assigns when you register. This is different from your:
- HMRC username or email address
- Companies House authentication code
- UTR (Unique Taxpayer Reference)
**How to find your correct Gateway User ID:**
1. Go to www.gov.uk/log-in-register-hmrc-online-services
2. On the sign-in page, look for the 12-digit User ID — it is printed on your Government Gateway enrolment letter, and is also shown in your account settings once signed in
3. Enter that 12-digit ID into the "Government Gateway User ID" field in TinyTax (under HMRC credentials)
4. Make sure Corporation Tax is listed as an enrolled service on the account — if it is not, you will need to add it before you can submit
If you are still seeing Error 1046 after updating the credentials, our support guide at https://tinytax.co.uk/support/hmrc-error-1046 covers all the common causes including enrolment steps and throttle/lockout recovery.