First CT600 when trading started after incorporation: which accounts to attach

1. Why the dates differ

Your statutory accounts can start on incorporation even if the first Corporation Tax accounting period starts later. HMRC explains that a company can be dormant for Corporation Tax between incorporation and starting its trade. Its first-year example has accounts from 11 May 2024 to 31 May 2025 and a trading return from 22 July 2024 to 31 May 2025. Another taxable activity can bring a company within the charge earlier, so the first customer payment is not automatically the tax start. See HMRC on accounting-period starts.

Check your HMRC business tax account and CT603 notice. If the dates appear wrong, call HMRC to resolve them. Changing a date only in filing software does not change HMRC's record.

2. Which accounts go with the CT600

Attach the full statutory accounts for the period overlapping the return, even when the CT600 starts later. HMRC requires the full accounts prepared for members, including the profit and loss account, rather than the filleted Companies House copy. CT600 box 85 indicates that the accounts cover a different period from the return. For example, if first accounts run from 1 June 2024 to 31 May 2025 and HMRC's Corporation Tax period begins on 1 July 2024, keep the accounts start at 1 June. See when CT600 and accounts dates differ.

3. Costs before trading began

Keep costs in their normal profit and loss lines of the full accounts. For tax, qualifying pre-trading revenue costs are treated as incurred when trading starts. They must be for the trade, incurred within the preceding seven years, and deductible had they been incurred after trading began. Trading stock bought before the trade and capital costs such as company formation fees do not qualify for this pre-trading expenses deduction. You or your accountant decide how each cost is treated. See the pre-trading expenditure guide.

If a cost is already in this year's expense figures, do not enter it again in Qualifying pre-trading expenditure. Add a cost that is included in the accounts but not deductible for Corporation Tax to Disallowable expenses.

Example: first accounts include £10,000 income and £400 of June costs before a 1 July trading start. Of the costs, £350 qualifies and £50 is a formation fee. The accounts show £9,600 profit. Adding back the £50 gives £9,650 trading profit before other adjustments. Excluding the £350 from expenses and deducting it separately would give the same tax profit, but would not show the full costs in these accounts.

4. If the first accounts cover more than 12 months

One Corporation Tax accounting period cannot exceed 12 months. Where the HMRC coverage needs two returns, SimpleCompanyTax#Simple CompanyTax divides the entered profit and loss figures, including costs from before trading, between the returns by days. Dividing a period of account's profit by days is the usual method under CTA 2009 section 52, which HMRC accepts. Costs already included in these accounts are part of those figures. Do not enter them again in Qualifying pre-trading expenditure.

Qualifying costs expensed in an earlier set of accounts instead use the separate Qualifying pre-trading expenditure field and its customer-entered split. Read how two CT600 returns cover a long first period and how the separate claim is allocated.

5. Enter the dates and figures

In SimpleCompanyTax#Simple CompanyTax, follow these steps for a supported HMRC-only filing:

1. In step 1, under What are you filing?, select HMRC CT600.
2. Enter the full first Accounts dates, then select My HMRC Corporation Tax period is different from my statutory accounts period.
3. Enter the Corporation Tax period start and Corporation Tax period end confirmed by HMRC. Complete the confirmations shown for those dates.
4. In Financial data, enter the full accounts figures under Profit & loss, using relevant rows such as Cost of raw materials and consumables, Staff costs and Other charges.
5. In Tax adjustments, leave Qualifying pre-trading expenditure blank for costs already in the expense rows. Enter costs that are not tax deductible in Disallowable expenses.
6. Choose Next, then Review filing and Preview your documents (free).

See the separate-period setup guide. A property-only company uses the property income and expense controls it is shown. The trading pre-trading and disallowable-expense controls are hidden for that case.

6. Check the documents

Check the return dates, both returns if shown, the full accounts period, the tax computation and the accounts attachment. In first accounts, the profit and loss reserve should reconcile to profit after tax carried into the balance sheet. Confirm that a pre-trading cost appears once, rather than in both an expense row and the separate deduction.

This is general guidance. Your company or its accountant decides which expenses qualify and whether another activity brought it within Corporation Tax before trading.

Official sources

• GOV.UK: trading after incorporation
• GOV.UK: check your Corporation Tax accounting period
• Finance Act 1998 Schedule 18 paragraph 11 and HMRC: full accounts to deliver
• CTA 2009 section 61 and HMRC: qualifying pre-trading costs
• CTA 2009 section 52 and HMRC: day apportionment
• HMRC: CT600 box 85