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How to submit your Corporation Tax return online, step by step

Filing your Corporation Tax return (CT600) with Taxley takes seven steps: create an account, enter your company details, profit and loss and balance sheet, check the Corporation Tax we calculate, review the iXBRL accounts we prepare, declare and pay the one-off fee, submit to HMRC with your own Government Gateway login, then check HMRC accepted it. Preparing is free; you pay only when you file.

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Last reviewed

Time
About an hour
Difficulty
Straightforward companies
Tools you’ll use
A Taxley account · Government Gateway login (to file with HMRC)
Have ready
Company figures (profit and loss and balance sheet) · Company UTR · Company registration number (CRN)

The process

Submit Corporation Tax return to HMRC in seven steps

  1. Step 1: Create an account and start a filing

    Sign up, then start a new filing. Choose your accounts type — micro (FRS 105) or small (FRS 102 §1A) — and your accounting period.

  2. Step 2: Enter company, P&L and balance sheet

    A guided, saveable wizard captures your company details (CRN, UTR, registered office), your business P&L (income — trading turnover or rental, allowable expenses, finance costs) and what the company owns and owes. You can leave and resume anytime.

  3. Step 3: We work out your Corporation Tax

    Taxley calculates your taxable profit and Corporation Tax — the right rate for your profit level, with marginal relief applied automatically — and shows a line-by-line schedule you can check.

  4. Step 4: We prepare your accounts

    Taxley produces your statutory accounts (FRS 105 or FRS 102 §1A) and tax computations, and validates everything automatically before you see it. Behind the scenes, this means generating the inline XBRL (iXBRL) files HMRC requires, tagged to the FRC taxonomy — validation fails loudly if anything is wrong.

  5. Step 5: Declare and pay

    Confirm the director declaration (CT600 boxes 975/980/985) and pay the one-off filing fee securely via Stripe — charged before the final filing is produced. The fee covers filing with HMRC and filing your accounts at Companies House.

  6. Step 6: Submit Corporation Tax return to HMRC

    Submit your CT600 + accounts to HMRC with your own Government Gateway login — filing is live. Then file the accounts at Companies House from the same filing page, using your company's Companies House authentication code, at no extra cost.

  7. Step 7: Check HMRC accepted your return

    Your Taxley filing page shows “Accepted by HMRC” with the date and time, and Taxley emails you HMRC’s correlation ID to keep for your records. If HMRC rejects the return, the email says what HMRC reported so you can correct it and resubmit — your deadline still applies. Download copies of everything filed, with a full audit trail. Filing is separate from paying: pay any Corporation Tax due to HMRC yourself.

What gets filed

What HMRC receives

  • CT600 return

    The Company Tax Return itself — every box worked out from your figures and checked before it is sent.

  • iXBRL accounts

    FRS 105 / FRS 102 §1A

    Your company’s statutory accounts, tagged with the FRC taxonomy so HMRC’s systems can read every figure.

  • Tax computation

    How your accounts profit becomes taxable profit and the tax due — rates, marginal relief and adjustments.

Plus your HMRC receipt and a full audit trail, kept in your account.

Worked example

What does filing look like for a typical small company?

Take a fictional company with a year ending 31 March 2026, no associated companies and taxable profits of £40,000. Its Corporation Tax is £7,600, at the 19% small profits rate, because its profits are no more than £50,000. You see that figure in Taxley before you pay anything.

Corporation Tax for the year
£7,600
Pay HMRC by
1 January 2027
File the CT600 with HMRC by
31 March 2027
File accounts at Companies House by
31 December 2026

In Taxley you enter the year's figures once. Taxley prepares the CT600, the tax computation and the iXBRL accounts from them, and you check each one. When you file, the return goes to HMRC with your Government Gateway login and the same accounts go to Companies House, for one fee. The deadline calculator and Corporation Tax calculator work out the same figures for your own company.

Before you start

Useful to read first

Frequently asked questions

Which accounting periods can Taxley file?

Taxley files returns for UK-resident micro and small companies, including older years back to accounting periods that started on 1 April 2020.

What do I need before I start?

The company's figures for the period (profit and loss account and balance sheet), its Unique Taxpayer Reference (UTR), its company registration number and the company's Government Gateway login to file with HMRC. To file the accounts at Companies House, you also need the company's 6-character authentication code. A straightforward return takes about an hour.

How does payment work?

Preparing and previewing is free. When you're ready, you confirm the director declaration and pay one fee for the return through Stripe, before the final filing is produced. The fee also covers filing the accounts at Companies House. The company pays any Corporation Tax due to HMRC itself; Taxley doesn't take tax payments.

How do I know HMRC accepted my return?

Your filing page shows “Accepted by HMRC” with the date and time, and Taxley emails you HMRC’s correlation ID to keep. If HMRC rejects the return, the email says what HMRC reported so you can correct it and resubmit; your deadline still applies. Acceptance means HMRC received a valid return, not that it has checked your figures.

Good to know: Corporation Tax returns are filed live to HMRC using your own Government Gateway login — paying your Corporation Tax is always done by your company directly to HMRC. Companies House accounts filing is live too: once the return is paid and the accounts are finished, press “File accounts at Companies House” on your filing page. You'll need your company's authentication code, which you save once on the company page. The service is still maturing, so review the flagged figures carefully before you file.

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