How to set different CT600 dates from Companies House

Short version. To set CT600 dates that differ from your Companies House accounts, choose HMRC CT600 under “What are you filing?” in step 1. Enter the full annual accounts dates, select “My HMRC Corporation Tax period is different from my statutory accounts period”, then enter the Corporation Tax start and end dates. The tax end can be earlier than, or equal to, the accounts end.

1. Before you start

If the first CT600 was already filed with the full accounts and only the second short period remains, use the second-return filing guide. Do not confirm no earlier taxable activity if the company was trading during the first period.

Have your accounts dates and the actual HMRC tax period ready. If you are unsure whether they should differ, read when CT600 and accounts dates can differ. For incorrect HMRC records, follow the date-correction checklist first.

This option is available for supported HMRC-only filings, including a later year. It does not file your annual accounts at Companies House. Those accounts still need to be filed separately when required. The full accounts are included in the HMRC filing package.

2. Enter the two date pairs

1. Choose the full annual accounts period in step 1. Keep its statutory start and end.
2. Select the separate Corporation Tax period option.
3. Enter “Corporation Tax period start” and “Corporation Tax period end”. Both dates are required.
4. Check that the tax start is on or after the accounts start, and the tax end is on or after the tax start and no later than the accounts end.
5. Read the return-count preview and complete the two confirmations before continuing.

For example, accounts might cover 1 January to 31 December 2025 while the confirmed tax period covers 1 April to 30 September 2025. Enter the full accounts pair first and the shorter tax pair second. Do not shorten the annual accounts dates to make the CT600 fit.

A selected tax span longer than 12 months produces separate CT600 periods through our existing split-return workflow. Read the long-period guide if the preview shows two returns.

3. Enter figures for the CT600 dates

For this workflow, all entered income, expenses and tax amounts must relate to the selected Corporation Tax span. We use those amounts in full. We do not multiply them by the proportion of accounts days covered by the shorter span.

With accounts covering January to December and tax covering April to September, £60,000 turnover and £12,000 expenses are still £60,000 and £12,000 in the tax inputs. The accounts must remain complete for January to December. Do not remove later activity from full annual accounts so you can make the confirmation.

Balance-sheet figures are different: they remain balances at the statutory accounts end. Existing rules for qualifying pre-trading expenditure, dated transactions and brought-forward amounts still apply. Short-period tax limits and any financial-year or two-return calculations also continue.

The page asks you to confirm that the dates match your CT603 notice or HMRC business tax account. It also asks you to confirm the company's position between the accounts start and a later Corporation Tax start. These checks support the date selection. They do not determine whether an earlier end is legally correct. HMRC sets out the events that end a tax period.

Beside the dates, we state that all income, expenses and tax amounts entered must cover the selected Corporation Tax period. This is guidance rather than an additional checkbox because you make the correctness and completeness declaration before filing with HMRC.

4. Check the documents before filing

Continue through the financial step, then choose “Review filing” to save your answers and prepare the review. Check the documents before submitting to HMRC.

• The CT600 and tax computation should show the selected tax dates, or the individual return dates where the span splits.
• The annual accounts should show their full statutory period and balance-sheet date.
• The CT600 “accounts for a different period” indicator, box 85, should reflect the date difference. See HMRC's CT600 instructions.
• Check payment and filing dates separately. See the deadline explanation.

5. If you cannot continue

I cannot see the separate-date option.

Check the filing choice. It is offered for HMRC CT600 only, not Companies House only or a combined filing.

The tax estimate disappeared.

Complete both tax dates and correct any range error. An incomplete pair cannot produce a current preview.

My confirmations became unticked.

Changing period dates withdraws the confirmations. Read and confirm them again for the new dates.

The tax end changed after I edited the accounts end.

An end that matched the previous accounts end follows the new accounts end. An explicitly earlier end is preserved, but still has to fit within the accounts period.

How do I save my changed dates?

Choose “Review filing” after completing the steps. “Next” moves you through the wizard. “Save Progress” keeps your progress in the current browser session so you can return to it there.

This describes the supported SimpleCompanyTax workflow. It is general guidance, not a determination of your company's tax periods or entitlement to relief.