Quick answers
- When is the company tax return deadline?
It is 12 months after the end of the accounting period the return covers. - Is the CT600 deadline the same as the Companies House accounts deadline?
No. The Company Tax Return goes to HMRC and is due 12 months after the accounting period ends. - What is the penalty for a late Company Tax Return?
GOV.UK shows £200 at 1 day late and another £200 at 3 months. - Do I need to file a Company Tax Return if there is no tax to pay?
Yes, if HMRC has sent a notice to deliver a Company Tax Return.
In more detail
The return is filed with HMRC, usually on form CT600 with your accounts and tax computations.
It is a different deadline from your Companies House accounts, and a different deadline from paying the tax.
Below you can see how the dates fit together, what HMRC charges if the return is late, and why you must file even when no tax is due.
When is the company tax return deadline?
The company tax return deadline is 12 months after the end of the accounting period the return covers. GOV.UK says this applies to every Company Tax Return (CT600) you are asked to file. The accounting period cannot be longer than 12 months, so each return has its own deadline.
An accounting period is normally the same as the financial year covered by the company's annual accounts.
If your accounts cover more than 12 months, for example a long first period, you must file 2 returns to cover them. Each return has its own deadline, based on its own accounting period.
Three different dates for the same year
Many directors mix up three dates. Paying Corporation Tax is due 9 months and 1 day after the end of the accounting period. That is before the return is due. Filing the return with HMRC is due 12 months after the period ends. The Corporation Tax payment deadline has its own rules for weekends and larger companies.
| What | Who it goes to | Usual deadline |
|---|---|---|
| Accounting period ends | 31 March 2026 | |
| Annual accounts (private company, not first accounts) | Companies House | 31 December 2026 |
| Pay Corporation Tax | HMRC | 1 January 2027 |
| File the Company Tax Return (CT600) | HMRC | 31 March 2027 |
Companies with taxable profits over £1.5 million pay in instalments instead, on different dates. This page covers the usual single payment.
Annual accounts go to Companies House on their own deadline. For a private company, later accounts are normally due 9 months after the financial year ends. See when dormant company accounts are due for the Companies House dates in full, including first accounts.
These dates are an illustration only. Always check the dates on your own HMRC and Companies House records.
Source: Pay your Corporation Tax bill
Do you have to file a Company Tax Return if no tax is due?
Yes. If HMRC sends your company a notice to deliver a Company Tax Return, the company must file one, even with no tax to pay. GOV.UK says you must still send a return if the company made a loss or has no Corporation Tax to pay. A nil return still answers the notice.
Having no tax to pay does not stop the late filing penalties below. The first penalties are fixed amounts, so they apply even when no tax is owed.
If your company has stopped trading and has no other income, you can tell HMRC it is dormant for Corporation Tax. GOV.UK says you then do not need to file another Company Tax Return, unless HMRC sends a further notice to deliver one.
If you have already received a notice to deliver a return, GOV.UK says you still need to file that Company Tax Return online. It will show HMRC the company was dormant for that period. Our guide to the HMRC notice to file a Company Tax Return explains what to do with the letter.
HMRC late filing penalties for the Company Tax Return
HMRC charges penalties if the return arrives after the deadline. The amounts below are from HMRC's GOV.UK page, checked on 6 October 2026.
| Time after the deadline | Penalty |
|---|---|
| 1 day | £200 |
| 3 months | Another £200 |
| 6 months | HMRC estimates the Corporation Tax bill and adds 10% of the unpaid tax |
| 12 months | Another 10% of any unpaid tax |
| Late 3 times in a row | Each £200 penalty becomes £1,000 |
If the return is late 3 times in a row, the £200 penalties rise to £1,000 each. These amounts apply to returns with a filing date on or after 1 April 2026. For returns due before then, the fixed penalties were £100, another £100 at 3 months, and £500 each if late 3 times in a row.
At 6 months late, HMRC writes to tell you how much Corporation Tax it thinks you must pay. This is called a tax determination. You cannot appeal against it. The way to replace it is to file the actual return.
Companies House penalties are separate
Companies House and HMRC are separate bodies. You file accounts with Companies House and your Company Tax Return with HMRC. They are two filings with two deadlines. Sending accounts to Companies House on their own does not file your Company Tax Return.
A company that is late with both can receive two separate penalties for the same year. Paying or appealing one does nothing to the other. See Companies House late filing penalties for the Companies House side.
Source: Prepare and file annual accounts for a limited company
How do you file the return and appeal a penalty?
You file a Company Tax Return online using commercial software, or an agent can file it for you. GOV.UK says filing by post is only allowed if you have a reasonable excuse or are filing in Welsh. HMRC's own online service for filing accounts and the Company Tax Return closed on 31 March 2026.
GOV.UK points to a list of commercial software suppliers you can use instead. Here is how to file a Company Tax Return now HMRC's service has closed.
When you file, you work out the company's profit or loss for Corporation Tax and its Corporation Tax bill. GOV.UK notes this profit or loss is different from the one shown in your annual accounts.
If you have a reasonable excuse for filing late, you can appeal against the late filing penalty online. You must file the Company Tax Return before you appeal. You will need the company's Unique Taxpayer Reference (UTR), the date on the penalty notice, the penalty amount and the end date of the accounting period.
Source: Filing company accounts and tax returns if you previously used the HMRC online service
Common Company Tax Return deadline mistakes
Treating the Companies House accounts deadline as the tax return deadline, or the other way round. They are different dates and different organisations.
Paying the tax late because the return is not due yet. For most companies, payment is due almost 3 months before the return.
Not filing because the company made a loss or had no tax to pay. If HMRC has sent a notice to file, the return is still due.
Forgetting that a long first period of accounts needs 2 tax returns.
Extending the company's financial year without telling HMRC before the original filing deadline. GOV.UK warns this can lead to a late filing penalty.
What SimpleFilings can and cannot do
SimpleFilings does not prepare or file Company Tax Returns. If you cannot find the company's UTR, we can request a copy from HMRC for a £4.99 SimpleFilings service fee. If your company has not traded, we can help you tell HMRC it is dormant for Corporation Tax. We can also prepare and file qualifying dormant accounts with Companies House. Any penalties already charged by HMRC or Companies House are separate and are not covered by our fee.
Frequently asked questions
When is the company tax return deadline?
It is 12 months after the end of the accounting period the return covers. An accounting period cannot be longer than 12 months, so long accounts need 2 returns.
Is the CT600 deadline the same as the Companies House accounts deadline?
No. The Company Tax Return goes to HMRC and is due 12 months after the accounting period ends. A private company's later accounts are normally due at Companies House 9 months after its financial year ends.
What is the penalty for a late Company Tax Return?
GOV.UK shows £200 at 1 day late and another £200 at 3 months. At 6 and 12 months HMRC adds 10% of any unpaid tax each time. If the return is late 3 times in a row, each £200 penalty becomes £1,000. These amounts apply to returns with a filing date on or after 1 April 2026. For returns due before then, the fixed penalties were £100, another £100 at 3 months, and £500 each if late 3 times in a row.
Do I need to file a Company Tax Return if there is no tax to pay?
Yes, if HMRC has sent a notice to deliver a Company Tax Return. GOV.UK says you must still send a return if you make a loss or have no Corporation Tax to pay.
When do I pay Corporation Tax?
GOV.UK says 9 months and 1 day after the end of the accounting period. That is earlier than the deadline for filing the return. Companies with taxable profits over £1.5 million pay in instalments instead.
Can I still file through HMRC's own online service?
No. HMRC's File your accounts and Company Tax Return service closed on 31 March 2026. From 1 April 2026 GOV.UK says to use commercial software, or an agent can file for you.
Can I appeal an HMRC late filing penalty?
Yes, if you have a reasonable excuse. You can appeal online, but you must file the Company Tax Return first.
Official sources
10
- Company Tax Returns
- Company Tax Returns: penalties for late filing
- Increases to Corporation Tax late filing penalties
- Accounting periods for Corporation Tax
- Pay your Corporation Tax bill
- Dormant companies: dormant for Corporation Tax
- Filing company accounts and tax returns if you previously used the HMRC online service
- Filing your accounts and Company Tax Return
- Prepare and file annual accounts for a limited company
- Find your UTR number
Written and checked by SimpleFilings against these official pages. Last checked . SimpleFilings is operated by ONAF Limited (company number 12589383), an independent firm, not part of Companies House, HMRC or the government.