Your company traded. Here is what you have to file, with or without tax to pay.

By Max Szolcek, founder of Dormant Return. Last updated 2 October 2026

A common situation: the company did some business, perhaps very little, and you have already filed micro-entity accounts at Companies House. Whether the year ended in a loss, broke even, or made a small profit, HMRC still needs a full Company Tax Return. If HMRC has issued a notice to deliver one, it is due whether or not there is tax to pay, and the late filing penalties are the same either way.

What HMRC needs from a company that traded

A Company Tax Return is not just the CT600 form. For a company that traded, HMRC's online service will only accept a return that contains all three of these, submitted together:

The CT600 itself, with turnover, the profit or loss for tax, any tax due and the financial-year split when the period straddles 31 March. Box 780 reports a trading loss arising in the period; box 285 reports brought-forward losses claimed against a profit; box 690 reports the annual investment allowance.
The accounts, tagged in iXBRL. For a micro-entity these are the same accounts you filed at Companies House: an income statement and a balance sheet.
A tax computation, also in iXBRL, showing how the accounts figure becomes the taxable profit or loss: add back depreciation and entertaining, take out bank interest, deduct any annual investment allowance, set off brought-forward losses, and arrive at the tax.

The computation is the part that catches people out. A dormant company can skip it by declaring itself dormant on the CT600. A company that traded cannot: there is no "nothing to pay" reason code, so a return without a computation is rejected before it is even looked at.

Deadlines and penalties

The return is due 12 months after the end of the accounting period. Any tax is due earlier, nine months and one day after the period end, and HMRC charges interest from that date if it is paid late. Miss the filing deadline and the flat penalties start at £100, rising to £200 after three months, then to a percentage of the tax and higher flat amounts for repeat lateness. See late CT600 penalties: the ladder applies even when no tax is due.

Keep your returns and tax computations as evidence of unused trading losses. These can generally be carried forward while the trade continues and reduce tax in a future profitable year. See HMRC's guidance on carrying forward Corporation Tax losses.

If the company made a profit

A small company pays Corporation Tax at the small profits rate of 19% on its taxable profit, as long as that profit is no more than £50,000 for a 12-month period (less for a shorter one) and the company has no associated companies. Above the limit, marginal relief applies and the sums get more involved. When an accounting period straddles 31 March the profit is split between the two financial years by days; at 19% in both, the total does not change.

Taxable profit is not the accounts profit. Depreciation and client entertaining are added back, bank interest is taxed separately as non-trading income, the annual investment allowance on equipment bought in the year comes off, and unused trading losses from earlier years are set against what is left. A company with £630 of sales and £600 of costs has a taxable profit of £30 and a tax bill of £5.70. It still has to be filed.

Filing the return does not pay the tax. You pay HMRC yourself, at gov.uk/pay-corporation-tax, quoting the 17-character payment reference from the notice to deliver or the company's business tax account.

What you need before you start

The micro-entity accounts you filed at Companies House (turnover, costs, the result, and the balance sheet lines).
The two figures the accounts do not show but the computation needs: how much of "other charges" was client entertaining, and any other cost that was not wholly for the business. Both are added back for tax. Depreciation is added back too, but that is already a line in the accounts.
The cost of any equipment bought new for the business in the period (a laptop, tools, furniture: plant and machinery, not cars or buildings). It is claimed in full as annual investment allowance.
The unused trading-loss balance from your previous tax computation, if there is one.
The company's 10-digit Corporation Tax UTR.
A Government Gateway sign-in with a Corporation Tax enrolment for the company.

Who Dormant Return can file for

Alongside dormant returns, Dormant Return files the return of a small trading company for £15, whether the period made a loss, exactly nil, or a profit taxed wholly at the small profits rate. You re-key the figures from the accounts already filed at Companies House; we generate the CT600, the iXBRL accounts and the iXBRL computation from them, work out any tax due, and file all three to HMRC under your own Government Gateway sign-in. HMRC's acceptance receipt is emailed to you with a PDF of the accounts, and if tax is due the receipt says how much and by when.

All of the following must be true:

A UK private company limited by shares, UK resident, not in a group and with no associated companies.
Micro-entity accounts covering the period already filed at Companies House.
One UK trade, and no income other than that trade and bank interest: no property income, no dividends received, no chargeable gains.
Accounts covering no more than 18 months, ending on or before 31 March 2026 (HMRC has not yet published the computation taxonomy for later period ends; this date will move when it does). Accounts longer than 12 months are filed as two returns, as HMRC requires, and each return is taxed on its share of the figures by days. See why a long first year means two returns.
A trading loss, exactly nil, or a taxable profit of no more than £50,000 for the period (less for a period shorter than 12 months), so any tax is at the small profits rate with no marginal relief.
No claims other than the annual investment allowance on equipment bought new in the period from an unconnected person: plant and machinery only, no cars, no buildings, no earlier-year pool balances, nothing sold or scrapped in the period. No other capital allowances, no R&D or creative-industry relief, no group relief, no carrying a loss back to an earlier year.
Any brought-forward trading losses are established unused tax losses already reported to HMRC, all arising on or after 1 April 2017 from the same continuing trade, with no change of ownership or loss restrictions.

To start, enter your company name on the home page, then choose Company not dormant? under the company field. A short checklist confirms the above before any figures are asked for, and the page shows the tax as you type.

If you have brought-forward trading losses, enter the full unused balance from your previous Corporation Tax computation, separately from the accounting figures. In a loss-making or nil year the balance is carried forward together with the new loss: £50,611 brought forward plus £4,205 arising gives £54,816 carried forward. In a profitable year the balance is set against the profit automatically, up to the amount of the profit, and only the remainder is taxed: £50,611 brought forward against a £7,100 profit means no tax and £43,511 carried forward. Losses arising before 1 April 2017, uncertain balances, ownership changes or restricted losses need general tax software or an accountant.

The profit and loss reserve in your Companies House accounts is an accounting balance and may differ from your tax losses. Adding a tax-loss schedule does not itself require changing accounts already filed at Companies House. Where tax is due, the accounts we file show that tax charge on the income statement, so the profit after tax can differ from the accounts you filed at Companies House if those showed no tax.

One honest limit: the only capital allowance we claim is the annual investment allowance on equipment bought new in the period. A company with older equipment in a capital allowances pool, or one that sold an asset, may be able to reduce its bill further with an accountant. Nothing we file ever understates the tax.

Who it cannot file for, and where to go instead

If any line above is not true, the return needs boxes and computations this service deliberately does not produce: marginal relief above the small profits limit, capital allowance pools and disposals, other reliefs, losses carried back, property or investment income, group matters. Two good routes:

1. General Corporation Tax software

HMRC publishes a list of commercial software suppliers for Corporation Tax. Look at the "Produce and submit CT600" table for products marked "Suitable for self-filers". One-off returns from self-filer packages typically cost between roughly £20 and £100.

2. An accountant

The right choice when there are allowances or reliefs worth claiming beyond the annual investment allowance, when profits are above the small profits limit, or when you want someone to check the accounts and the figures before they are committed to HMRC.

Traded, with a loss, nil or a small profit? Dormant Return builds the CT600, iXBRL accounts and tax computation from the figures you already filed at Companies House, works out any tax due, and files them to HMRC. £15 one-off, refunded automatically if HMRC rejects the return.

Start your return