Can I file only the second CT600 if the first return is already filed?
Short version. Yes. If the first CT600 has already been filed and HMRC still requires a return for the second short period, you can file that outstanding return separately. You do not need to submit the first return again just to complete the second. How you handle the accounts depends on whether the full accounts were included with the first return.
1. Why does HMRC want a second short-period CT600?
A Corporation Tax accounting period cannot exceed 12 months. First statutory accounts often cover a little longer, so a company trading throughout that time normally needs two CT600 returns. The second covers the remaining days or weeks and is sometimes called a stub period. See HMRC's explanation of first accounts and tax returns.
For example, a company incorporated and trading from 15 July 2024, with accounts ending on 31 July 2025, has:
- Full accounts: 15 July 2024 to 31 July 2025.
- First CT600: 15 July 2024 to 14 July 2025.
- Second CT600: 15 July 2025 to 31 July 2025.
If trading started later, the tax dates may differ. Read dormant at first, then trading. For the full two-return process, see first accounts longer than 12 months.
2. Do I need to amend or resubmit the first CT600?
Filing the outstanding period is a separate original return. An amendment corrects a return already filed. Completing the second period does not, by itself, call for an amendment to the first.
Use the second period's start and end dates. Do not try to replace both periods with one 13-month CT600. Box 50 concerns multiple returns being filed at the same time, so a second return filed on its own does not need that box simply because it belongs to a longer set of accounts. See the CT600 guide on return dates and box 50.
3. Can I file the second CT600 without attaching accounts again?
There is a specific accounts-omission reason for a period of account that differs from the tax period, with accounts supplied with a separate return. HMRC's manual tells its staff to check that other return for the accounts and assess whether the filing obligation is satisfied.
This supports an accounts-already-supplied route. It does not make accounts optional for every CT600. If the first filing included the full accounts covering both periods, suitable software can explain their omission from the second. If it did not, this route does not apply.
A blank attachment with no explanation is not the same thing. For an active company, keep the tax computation for the second period attached. The CT600 guide explains accounts, computations and box 90.
4. What figures go in the second return, and what if it made a loss?
Prepare the figures for the second period and any applicable tax adjustments or brought-forward balances. Avoid entering the full accounts-period totals into software that asks for short-period figures. The computation explains how the figures in the return relate to the accounts.
A loss does not remove a notice to file. HMRC says you must file when it requires a Company Tax Return, even if there is no profit or tax to pay. See Company Tax Returns. Paying the first period's tax also does not file the second return. Read filing a CT600 after paying Corporation Tax.
Can a dormant company file only the second CT600? Yes, if HMRC requires that remaining return and the first CT600 included the full accounts. Keep your trading status as Dormant. You do not need to select Active to use this option. HMRC explains when dormant companies still need to file a return.
5. How do I file only the second CT600 using different software?
Choose software such as SimpleCompanyTax to file only the second CT600 when the first has already been filed elsewhere. Our remaining-return option uses the short-period dates and handles accounts already supplied with the first return.
For an eligible company, start a new HMRC-only filing, enter the full accounts dates and choose File only the remaining CT600. Confirm that the first return included the full accounts and that the remaining dates match your HMRC account. Enter only the remaining period's figures. We prepare one original CT600 with no accounts attached. Active companies receive a computation. Dormant returns use the reason “Company dormant” for omitting computations. The first return is not resubmitted.
If the company traded during the first period, do not select a declaration saying there was no earlier taxable activity. That describes a different situation. Check supported company types before choosing your filing route.
This is general guidance. If the first return's contents or the tax treatment are uncertain, resolve that before relying on the accounts-already-supplied route.