How do I know HMRC has received my CT600?

In short: You know HMRC has your Company Tax Return (CT600) when your filing software shows HMRC's acceptance, with the correlation ID and HMRC's receipt. GOV.UK says that acknowledgment of receipt doesn't mean HMRC has agreed your figures (GOV.UK: Company Tax Return obligations). If no answer arrives, check the status before sending the return again. Taxley files the CT600 for £44.50 (promotion price until 31 Dec 2026; £89.00 from 1 Jan 2027) with micro-entity accounts and shows HMRC's answer on the filing page, then files the accounts at Companies House once the return is paid and finished.

Take the 30-second check to see whether Taxley fits your company, or start your return.

Key facts (checked on 1 October 2026)

How can you tell HMRC has received your CT600?

Look for HMRC's final answer, not just the fact that you pressed send. When an online return gets through, HMRC sends an acknowledgment of receipt (GOV.UK: Company Tax Return obligations), and filing software shows the return as accepted, with the correlation ID HMRC gave the submission. Without that, the return is still waiting or failed.

HMRC's protocol for online submissions explains the steps behind that answer. The software sends the return to HMRC's gateway, which replies with an acknowledgement and a correlation ID once it has checked the message header, including the sign-in. The software then checks back at intervals the gateway sets until HMRC sends its final response (HMRC: Transaction Engine Document Submission Protocol). Before HMRC sends a success response, it checks the return against its schema and business rules, and checks the IRmark, a code the software calculates from the return's contents. The success response then carries HMRC's digital receipt, which confirms acceptance and the IRmark. HMRC's IRmark specification calls the receipt the taxpayer's proof of submission, which can be used to challenge the copy HMRC holds (HMRC: IRmark specification). Keep that receipt, the correlation ID and the exact files you sent together.

What is the difference between HMRC's first acknowledgement and acceptance?

The first acknowledgement only says HMRC's gateway has taken the submission in and given it a correlation ID; it isn't a decision about the return. Acceptance comes in HMRC's final response, after the return has passed HMRC's checks, and carries HMRC's receipt (HMRC: Transaction Engine Document Submission Protocol).

Taxley's decision table: what each submission status means

A test acceptance is the easiest one to misread. HMRC's validation rules give test-in-live submissions their own message class, HMRC-CT-CT600-TIL, separate from the live class used for real returns (HMRC: Corporation Tax online service validation rules), and HMRC's IRmark specification says the receipt for a test-in-live submission carries advisory text instead (HMRC: IRmark specification). Only a live submission that HMRC accepts files the return. A rejection is the opposite case: HMRC refused that submission, so unless HMRC already holds a return for the period (error 3304), the deadline still runs. The guide to fixing a CT600 rejected by HMRC explains the error numbers, starting with the sign-in error 1046. First accounts longer than 12 months may require one or two returns, depending on trading dates and HMRC's notice (GOV.UK: first accounts and Company Tax Return). Check acceptance for every required return.

What does "accepted" mean for your CT600?

It means HMRC has received the return, not that it agrees with it. GOV.UK says the acknowledgment "does not mean that HMRC has agreed the figures provided in the return", and that HMRC can correct obvious errors or omissions and can enquire into the return (GOV.UK: Company Tax Return obligations).

The time HMRC has to open an enquiry depends on when you filed. For a return delivered on or before its filing date, HMRC can give notice of an enquiry up to 12 months from the day the return was delivered; for a company in a group that isn't a small group, the 12 months run from the filing date instead (FA 1998 Sch 18 para 24). A late return stays open longer. Acceptance doesn't pay the tax either. Corporation Tax is usually due 9 months and 1 day after the accounting period ends, before the return's own deadline, and must be paid electronically (GOV.UK: Company Tax Return obligations). The annual accounts also go to Companies House separately. The guide on what to do after your CT600 is accepted lists those tasks. If you find a mistake after acceptance, you can usually amend the return within 12 months of the filing deadline (GOV.UK: making changes); the guide to correcting a CT600 after filing covers how.

Where can you check that HMRC has your return?

Check three places in order: your filing software's status and HMRC's receipt, the company's HMRC business tax account, then HMRC itself. HMRC's business tax account guide says a tax card can show whether you have a return to complete, with links to return information (HMRC: business tax account guide).

Start with the software that sent the return, because the receipt and correlation ID come back to it. If an accountant filed, ask them for HMRC's acknowledgment and the filed copies; HMRC's guide says a company that uses an agent can still use its business tax account to check what's happening. To check the account, sign in with the company's Government Gateway user ID (GOV.UK: Sign in to your HMRC business tax account) and open the Corporation Tax card; the guide to the Government Gateway user ID for Corporation Tax helps if you can't find the sign-in. HMRC's Corporation Tax enquiries page offers a digital assistant, phone and post for general questions, and notes that HMRC's peak period for Corporation Tax returns runs from December to April. Have the company's 10-digit UTR ready, because HMRC's advisers can't give it to you over the phone. GOV.UK also says online services may be slow at busy times (GOV.UK: problems signing in).

What should you do if no confirmation arrives?

Don't send the return again straight away. Ask your software provider to confirm the submission's status, check HMRC's service availability page for known problems, and look at the business tax account. Resend only once you know the first return didn't arrive (HMRC: service availability and issues).

If the first return did arrive, a resend is rejected rather than filed twice. HMRC's validation rules reject a second original return for dates it already holds with error 3304, "Original return already received for this period", and say a change must be flagged as an amendment (HMRC: Corporation Tax online service validation rules). HMRC's protocol also has an error, 2005, for a submission whose acknowledgement from HMRC's back-end system didn't arrive in time; it tells software to resubmit or ask HMRC whether the submission was accepted (HMRC: Transaction Engine Document Submission Protocol). Asking first is safer when you can't see the outcome. Keep the correlation ID, the date and time you sent the return and any message on screen, because those let your provider or HMRC trace the submission. If the deadline is close, act the same day: a return filed one day late costs £200 (GOV.UK: Penalties for late filing), and GOV.UK lets you appeal a late filing penalty if you have a reasonable excuse.

What does Taxley show once you've filed?

Taxley (taxley.co.uk), UK online software that prepares and files the Company Tax Return (CT600) with HMRC and the annual accounts with Companies House, lists each HMRC submission on the return's filing page with its status, correlation ID and the date and time sent, and emails you HMRC's answer. HMRC's acknowledgment confirms receipt only (GOV.UK: Company Tax Return obligations).

Once HMRC accepts the return, the page's timeline shows "Accepted by HMRC" with the date and time, and the acceptance email gives the HMRC correlation ID to keep and reminds you that filing is separate from paying. While HMRC hasn't answered, the page says the return has been sent to HMRC and is awaiting HMRC's confirmation, asks you not to resubmit and checks the outcome automatically. If Taxley can't confirm the result, it says HMRC may already have received the return, asks you not to resubmit, and checks with HMRC before updating the page. For each submission you can download HMRC's final response and the first acknowledgement, alongside the CT600 that was sent. Test runs are labelled "TEST — nothing filed". A rejection shows HMRC's error numbers and its own wording.

How to submit your Corporation Tax return online, step by step shows the whole process, and you can take the 30-second check to see whether Taxley fits your company.

Frequently asked questions

How long does HMRC take to confirm a CT600?

HMRC's gateway tells filing software how long to wait between checks until the final answer is ready (HMRC: Transaction Engine protocol). GOV.UK warns online services may be slow at busy times, so a delay alone doesn't mean the return failed. Taxley says confirmation can take a few minutes, occasionally longer.

Is the correlation ID my HMRC receipt?

Not on its own. The correlation ID is the reference HMRC's gateway gives a submission so software can follow it up (HMRC: Transaction Engine protocol). HMRC's receipt comes with the acceptance and confirms the IRmark, a code that ties it to the exact return sent.

Does an accepted CT600 mean the Corporation Tax is paid?

No. Filing and paying are separate. Corporation Tax is usually due 9 months and 1 day after the accounting period ends, before the return's 12-month filing deadline, and must be paid electronically (GOV.UK: Company Tax Return obligations).

What if my accountant filed the return?

Ask the accountant for HMRC's acknowledgment and the filed copies, because the receipt comes back to the software that sent the return. HMRC's guide says a company using an agent can still use its business tax account to check what's happening (HMRC: business tax account guide).

Does a successful test submission count as filing?

No. HMRC's test-in-live submissions use their own message class, HMRC-CT-CT600-TIL, separate from live returns (HMRC: CT online validation rules). A successful rehearsal passes the test checks; live-only checks can still reject the return. Only live acceptance files it.

General information, not personalised tax advice. HMRC's submission process checked against HMRC's published specifications on 1 October 2026.