What documents do you need to file a company tax return?

What a Company Tax Return is made of

If HMRC sends your company a notice to deliver a Company Tax Return, you must file one. That still applies if the company made a loss or has no Corporation Tax to pay.

HMRC says a complete return is made up of:

• Form CT600. The return form itself, with the company's taxable profit and the tax due.
• Any supplementary pages. Extra pages for particular situations, such as loans to directors who are shareholders.
• Company accounts. The annual accounts for the period.
• Tax computations. The workings that turn the accounting profit into the profit for Corporation Tax.

The accounts and computations must be in a format called iXBRL. In practice that means filing online through commercial software. Paper filing is only allowed if you have a reasonable excuse or are filing in Welsh.

The return and the accounts you send to Companies House are separate filings with different deadlines. Our guide on the company tax return vs company accounts explains the difference.

The basics you need before you start

Whoever prepares the return will first need some simple details:

• The company's UTR. This is the 10-digit Unique Taxpayer Reference for Corporation Tax. It appears on the notice to file and on other HMRC letters.
• The company number. This is on the certificate of incorporation and the Companies House register.
• The accounting period dates. The return covers an accounting period, which is usually the same 12 months as the financial year. See what is my company's accounting period if you are unsure.
• Last year's accounts and return. These show figures that carry forward, such as losses not yet used and the value of assets for capital allowances.

The records behind the figures

The figures on the return come from the company's books. GOV.UK says a company must keep records of all money received and spent, assets it owns, debts it owes or is owed, stock at the year end and the stocktakings used to value it, and all goods bought and sold, with who they were bought from and sold to (unless it is a retail business). In practical terms, that means gathering the following.

Bank and payment records

• Statements for every business bank account, covering the whole period
• Statements for business credit cards, savings accounts and loan accounts
• Reports from payment apps and card terminals, if you take payments that way

The closing balance in your books should agree to each statement on the last day of the period. Our guide to bank reconciliation explains how that check works.

Sales and income

• Copies of every sales invoice raised in the period
• A list of customers who still owed you money at the year end
• Records of any other income, such as interest, grants or insurance payouts

Costs and expenses

• Purchase invoices and receipts for business costs
• A list of suppliers you still owed at the year end
• Bills that cover two periods, such as insurance or rent paid in advance

Not every cost reduces the tax bill. Some are added back in the computations. Our guide to allowable expenses for limited companies covers what normally counts.

Stock

If you hold stock, you need the count and value at the year end, plus the stocktake sheets used to reach that figure.

Assets

• Invoices for equipment, vehicles, machinery and computers bought in the period
• Details of any assets sold or scrapped, with the amount received
• A list of assets the company already owned

Asset purchases matter because of capital allowances. The Annual Investment Allowance is currently £1 million, but it cannot be claimed on business cars. Those get writing down allowances instead. Without the invoices, the right allowance is hard to work out.

Loans and finance

• Loan agreements and year end statements showing the balance and interest
• Hire purchase and finance agreements
• Details of money lent to or by directors

Payroll and dividends

• Payroll summaries for the period, showing wages, PAYE and National Insurance
• Pension contribution records
• Dividend vouchers and board minutes for any dividends paid

VAT records

If the company is VAT registered, bring the VAT returns for the period. The VAT account in the books should agree to what was filed and paid.

The director's loan account

This one causes more year end questions than most. If a director who is also a shareholder owes the company money at the end of the accounting period, it must be shown on supplementary form CT600A.

If the loan is not repaid within 9 months of the end of the accounting period, the company pays extra Corporation Tax on the amount not repaid in time, at 35.75% for loans made on or after 6 April 2026, 33.75% for loans made from 6 April 2022 to 5 April 2026, and 32.5% for loans made before 6 April 2022. That tax can be reclaimed once the loan is repaid, but the interest on it cannot.

So the preparer needs a clear record of every amount the director took out or paid in, with dates. Personal spending on a company card should be logged as it happens, not pieced together at the year end.

A worked example

Deadlines and late penalties

The Corporation Tax deadlines run from the end of the accounting period:

• Paying Corporation Tax. Usually 9 months and 1 day after the period ends. This comes before the filing deadline. See how to pay your Corporation Tax bill.
• Filing the return. 12 months after the period ends.

If the return is late, HMRC charges £200 one day after the deadline and a further £200 at three months. At six months, HMRC estimates the tax and adds 10% of the unpaid tax. At twelve months, it adds a further 10% of any unpaid tax. If the return is late three times in a row, the £200 penalties rise to £1,000 each.

Because tax is due before the return, the records really need to be ready within 9 months, not 12.

How long to keep the documents

Company records must normally be kept for 6 years from the end of the last company financial year they relate to. Some must be kept longer, for example where an asset is expected to last more than 6 years, the return was filed late, or HMRC has opened a compliance check.

A company that does not keep proper records can be fined £3,000 by HMRC, and its directors can be disqualified. Our guide on how long to keep business records covers the detail.

Make year end a short job

Most of the documents above are created during the year, not at the end of it. The hard part is rarely the return. It is finding a receipt from eleven months ago, or working out what a card payment was for.

If the books are reconciled as you go, with missing invoices chased while they are fresh, the year end pack is mostly ready on the last day of the period. Your accountant then works from clean figures. See what are year end accounts for the next step, or our page on bookkeeping for limited companies.