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How to file a CT600 if Corporation Tax is already paid

Last updated: 9 September 2026

Short version. Yes, you can file a CT600 after paying Corporation Tax. Payment and filing are separate steps. Complete the return using the company’s full figures, enter the relevant tax already paid in box 595 and check the resulting balance before submitting.

1. Do you still need to file if the tax is paid?

Paying HMRC does not deliver a Company Tax Return. If HMRC has sent the company a notice to file, you must address that filing obligation even if you believe nothing remains to pay. See HMRC’s Company Tax Returns overview.

For a company outside the instalment-payment rules, payment is normally due nine months and one day after the accounting period ends, while the return is normally due after 12 months. That is why paying before filing can be entirely normal. Check your actual deadlines rather than waiting for the filing deadline to pay.

2. Gather the right records

  • The accounting period dates and completed annual accounts.
  • The tax calculation and any adjustments or claims.
  • Corporation Tax payment dates, amounts and references.
  • The HMRC statement for the relevant period and details of any refunds.

Reconcile the payments before entering them. If a payment is missing from the expected HMRC period, check its reference and contact HMRC about the difference. Typing a figure into box 595 does not transfer money between HMRC periods.

3. Prepare the full return

Enter the company’s income, expenses, balance sheet and tax adjustments as usual. Do not subtract the payment from turnover or enter it as an extra operating expense to make the return show a lower tax bill. The accounts and tax computation still need to show the underlying result correctly.

For the meaning of each settlement box and a payment reconciliation example, read CT600 box 595 explained.

4. Enter Corporation Tax already paid

Use software that supports tax already paid for the return you are filing. The relevant entry is box 595. Your software should then calculate the reconciliation, rather than asking you to reduce taxable profit to reflect the payment.

For an eligible active micro-entity using SimpleCompanyTax:

  1. Open step 2 of the filing wizard and find Tax adjustments.
  2. Use the green 595 Corporation Tax already paid field. Its help icon explains which payments to include.
  3. Enter the payment amount in pounds and pence, excluding refunds. Leave it blank if there are no payments.
  4. Tick the checkbox labelled: I confirm that I supplied these tax already paid figures and checked that they are correct for these returns, excluding amounts HMRC has repaid.
  5. Review the calculated outstanding or overpaid amount and the draft documents.

We use the payment figures you provide. We do not fetch or verify your HMRC payment statement, and this entry does not ask for bank details. The payment fields are available for supported active-company filings, including where the calculated liability is nil. Dormant payment entry is not supported.

5. If the accounts cover two tax returns

A Corporation Tax accounting period cannot exceed 12 months, so longer first accounts can require two CT600s. In SimpleCompanyTax, click + 595 Corporation Tax already paid. Enter each period’s payment in the 595 Corporation Tax already paid field under Return 1 or Return 2, using the dates shown beside each heading.

Enter the payment belonging to each period separately. Collapsing the fields does not delete your entries. If you edit the dates, review the retained amounts and confirmation against the new dates. The software does not move or split payments for you.

6. Review, submit and check the balance

If the liability is £3,800 and the full £3,800 has been paid, an ordinary return with no other credits shows nothing outstanding. If only £2,000.25 has been paid, it shows £1,799.75 outstanding. You can still file the return with a balance to pay. See how partial payments and overpayments appear on a CT600.

Check the filing receipt after submission. Filing does not itself pay any remaining tax, and entering an overpayment does not guarantee an immediate refund. Check the current HMRC account for payments, interest or other amounts that may not be reflected in the return’s balance. Use HMRC’s payment service for any remaining bill.

7. Official guidance

This is general filing guidance. You remain responsible for the accuracy of your figures. Ask your accountant or HMRC if you cannot reconcile the payments or identify the correct period.