When HMRC refuses a Company Tax Return it sends back a short message, and the message rarely says what to do next. Most rejections have nothing to do with the figures: HMRC is objecting to who sent the return, which company it is for, or whether it should have been a new return or an amended one. This page explains each message you are likely to see in Tax Optimiser, why it happens and the fix.
First rule — don’t simply press Submit again. With one exception (a wrong password), every error on this page fails in exactly the same way the second time, and sending a return twice can create a new problem of its own.
Where the error appears
If HMRC rejects a return while you are in the submission wizard, the wizard shows There was an issue submitting the return with HMRC’s message and, for the errors below, an explanation and a button for the next step.
You can read it again later. Open the period, choose Corp Tax Submission and open the return. A rejected return has the status Error, and its Logs card lists each message exchanged with HMRC. Click Error on the red entry to see HMRC’s wording and the explanation.
The log normally shows an acknowledgement (HMRC has received the return) followed by either a response (accepted) or an error (rejected). A return is only filed once HMRC has accepted it.
Errors about new and amended returns
HMRC keeps one original return for each accounting period. Anything sent afterwards must be marked as an amended return, and an amended return is only accepted when there is an original to amend. Three errors come from getting this the wrong way round, or from running out of time.
3304: Original return already received for this period
What it means. HMRC already holds an original return for this company and period, so it will not take another. Nothing is wrong with the figures.
Why it happens. One of two things:
- The return was sent earlier and HMRC received it, even though you never saw it confirmed. This is the usual cause when HMRC was slow to answer and the return was sent a second time. HMRC may also email to say a submission was unsuccessful: that is normally the duplicate, not the copy it accepted.
- A return for the period was filed somewhere else, in other software or by a previous accountant.
What to do. If the return was sent from Tax Optimiser before, do not send it again: contact support so the accepted copy can be confirmed with HMRC and the return marked as filed. If the earlier return was filed elsewhere and these figures should replace it, click Submit as amended. See Amending a CT600.
1611: No original return yet recorded
HMRC’s wording is “No original Return yet recorded, please contact the HMRC Online Services Helpdesk”. A close relative reads “The accounting period of this amended return does not match the records currently held for the company”.
What it means. The return was sent as an amended return, and HMRC has no original for that period to amend. It is the mirror image of 3304.
Why it happens. Almost always, Is this an amended return? was set to Yes (or the wizard’s This is an amended submission box was ticked) on the first return for the period. You do not need to phone HMRC.
What to do. Click Start again as a new return. That clears the amended setting on the period and opens the wizard on a new return. Unticking the box in the wizard is not enough by itself, because the period would put it back.
If an original really was filed elsewhere, HMRC holds it under different dates. Compare the period dates on that return with this one; they must match exactly before an amendment is accepted.
CTISS002: Cannot file an amendment after the allowable due date
What it means. The time allowed for amending this return online has run out.
Why it happens. A company can amend its return up to 12 months after the filing deadline, and the filing deadline is normally 12 months after the end of the period. That gives about two years from the period end. For a year ended 31 March 2024 the last day was 31 March 2026.
What to do. Sending it again will never work. Tax Optimiser stops an amendment that is out of time before it is sent, and greys out Submit as amended with the closing date. To correct the return:
- if the company paid too much tax, see whether it can claim overpayment relief, which has its own four-year limit from the end of the accounting period;
- if it paid too little, tell HMRC about the underpaid tax;
- otherwise write to the Corporation Tax office, giving the company’s UTR, the accounting period and the figures being corrected.
Errors about who is filing and for which company
1046: Authentication failure
HMRC’s wording is “Authentication Failure. The supplied user credentials failed validation for the requested service.”
What it means. HMRC did not accept the Government Gateway details sent with the return, so it never looked at the return itself.
Why it happens. Check these three, in this order:
- Government Gateway user ID. It must be the ID that is enrolled for the Corporation Tax online service. An ID that is only used for VAT or PAYE fails, as does a personal ID.
- Government Gateway password. Type it in again. Passwords expire and get reset, and a saved password does not follow a change made on HMRC’s website.
- Corporation Tax UTR. It must be the 10-digit reference for this company, and the Government Gateway ID must be allowed to file for it. An accountant’s agent ID can only file for clients that have authorised the firm for Corporation Tax.
What to do. In the wizard, go Back to start and use the Update buttons beside HMRC Government Gateway credentials and Corporation Tax UTR, then submit again. Accountant firms can hold one set of credentials for the whole firm; choose where to save them when you update. A good test is to sign in at HMRC online services with the same ID and password and confirm Corporation Tax is listed.
The CRN on the submission does not match the CRN for this Unique Taxpayer Reference
What it means. HMRC links the UTR on the return to a different company registration number from the one sent, or to none.
Why it happens. One of the two identifiers is wrong. The common mistakes are another company’s UTR, or a director’s personal Self Assessment UTR, typed in place of the company’s. Less often the Companies House number on the period is wrong. For a newly formed company, HMRC’s own record may not be linked yet.
What to do. Check the UTR against a Corporation Tax letter from HMRC (how to find it) and the company number against the Companies House register. Correct the UTR on the first step of the wizard and submit again. If both are right, the company needs to ask the Corporation Tax helpline to correct its record before any return will be accepted.
Waiting for HMRC
This is not an error. HMRC acknowledges a return straight away and then checks it, which usually takes under a minute. When HMRC is busy it can take much longer. The wizard waits for two minutes, then shows Waiting for HMRC and lets you carry on with other work.
The return is listed with the status Submitting. Tax Optimiser asks HMRC for the answer every ten minutes, and you can ask at any time with Check with HMRC.
Heads up — a return that is waiting has been received. Do not send it again. Tax Optimiser will not send another return for the period until HMRC has answered this one, because a second copy would be rejected with 3304.
Stops before the return is sent
The first step of the wizard checks for problems HMRC is certain to reject. These cannot be overridden.
This return cannot be submitted yet
HMRC rejects a return for a period that has not ended. You can prepare the accounts and computation in advance, and send the return from the day the period ends. The one exception is a company in liquidation: choose that Company Type on the same step.
No director is selected to sign the balance sheet
The accounts sent to HMRC must name the director who approved the balance sheet. Open View Accounts, choose Directors and tick Signing for a director who was in office when the accounts were approved. A company secretary cannot sign the balance sheet.
The directors’ signage date has not been set
This is the date the board approved the accounts. Set it on the General tab of the Corporation Tax computation. If the return is declared on a later day, see CT600 declaration date.
HMRC Government Gateway credentials have not been saved
Click Add credentials on the first step and enter the Government Gateway user ID and password that are enrolled for Corporation Tax.
Common questions
HMRC emailed to say my submission was unsuccessful, but Tax Optimiser shows it as complete. Which is right?
Usually both. If a return was sent more than once, HMRC accepts the first copy and rejects the rest as duplicates, and it emails about the rejected ones. A status of Complete with an IR mark means HMRC accepted a copy.
Will I be charged again if I have to resubmit?
No. The submission fee is paid once for the period and covers every attempt, including amended returns.
Does a rejected return count as filed on time?
No. A return is filed when HMRC accepts it. If a deadline is close, fix the cause and send it again the same day rather than waiting.
The return is still Submitting after an hour. Should I send it again?
No. HMRC has received it. Use Check with HMRC, and if there is still no answer after a working day, contact support.
I get error 3304 but I have never filed this period. What now?
Check with any previous accountant, and look in the company’s HMRC online account for a return already filed for the period. If one is there, send yours as an amended return. If you are sure nothing was filed, ask the Corporation Tax helpline what HMRC holds.
The error is not on this page. What should I do?
Open the return, expand Logs and click Error to copy HMRC’s exact wording, then contact support with the company name and period. Messages that mention a box number are usually about the figures, and the CT600 box guide explains each box.