CT600 box 55: using estimated figures in a Company Tax Return

Last updated: 12 October 2026

Short version. Ticking box 55 tells HMRC that the return contains an estimated figure. It does not change any figure or the tax, and it does not send the final figures later for you. A Company Tax Return can contain estimated figures when final figures are not available. Enter the company's reasonable best estimate as a number, then tick CT600 box 55 to tell HMRC that the return contains an estimate. Do not enter wording such as "information to follow" instead of a figure.

Go to the steps and entry details

On this page

CT600 box 55Any period, including over 12 monthsWhere you see it: Financial Data › after Employees

Before entering figures, the filing setup questions can set the existing destination and CT600 route for an ordinary limited company. They keep the full accounts dates beside the CT600 dates. You can also continue with the controls below without opening the questions.

What this guide covers

Ticking box 55 tells HMRC that the return contains an estimated figure. It does not change any figure or the tax, and it does not send the final figures later for you.

The tick box This Corporation Tax return contains estimated figures is at the bottom of Financial Data, after the Employees section.
Ticking it shows Explanation of estimated figures, up to 4,000 characters. The field is optional in the wizard, but HMRC expects an explanation.
Your explanation appears in the downloadable tax computation PDF and, when an iXBRL computation is generated, in the computation sent with the CT600.
When your accounts period ends more than 12 months after it starts, even by one day, one tick and one explanation apply to both CT600s. Say which return an estimate relates to where that matters.

What CT600 box 55 means

Box 55 is labelled Estimated figures in HMRC's Company Tax Return guide, which says to enter an X in box 55 if estimates have been used. It is a disclosure about the figures already in the return. It is not a separate calculation and it does not replace any amount with an estimate for you.

Box 55 is different from box 50. Box 50 says that the company is making more than one return at the same time, which can happen for an accounting period longer than 12 months. Box 55 says that at least one figure in the return is estimated.

More help: HMRC CT600 guide: box 55 estimated figures · HMRC CT600 guide: box 50

When to tick box 55

Tick box 55 when the Company Tax Return includes a figure that is estimated rather than final. Examples include:

closing stock based on a year-end count and the best supplier-cost information available
turnover reconstructed from the records the company can obtain
a valuation that cannot be finalised before the filing deadline
information from a third party that is not yet complete

Use it if all of these are true

At least one figure in the return is an estimate because the final figure is not available.
The figure entered is the company's reasonable best estimate, as a number.
You can say which figures are estimated, why, and when final figures are expected, if known.

Do not use it if

A figure is only rounded in the normal way, or comes from ordinary accounting judgement in final accounts.That is not an estimated figure for box 55.
A filed return turns out to contain an error.Use instead: How to amend a CT600
You want to leave a figure out until the final figure arrives.See the common mistake below

Do not tick it merely because a figure is rounded in the normal way or because you used accounting judgement to prepare final accounts. The question is whether the return actually contains an estimated figure rather than a final one.

Use a reasonable best estimate

HMRC's CTM93280 guidance on estimated figures says an estimate should be reasonable and should represent the company's best assessment using the information available. Placeholder wording instead of a figure does not meet the filing obligation.

Keep the records and working that support the estimate. HMRC's guidance also addresses explaining why an estimate was necessary and, where appropriate, when the figure is expected to be final. #Simple CompanyTax provides an optional Explanation of estimated figures field beneath the box 55 tick box. Your words appear in the downloadable tax computation PDF and, when an iXBRL computation is generated, in the computation sent with the CT600. HMRC expects an explanation even though this field is optional in the wizard.

More help: HMRC CTM93280: estimated figures in returns

Common mistake: leaving the estimated part out until the final figure arrives

Box 55 does not add anything to a figure. An amount you leave out is filed as if it did not exist, and the tax is worked out without it. HMRC's manual expects the company's best estimate in the return, and says words such as "information to follow" instead of a figure do not meet the filing obligation. In this fictional example, part of the turnover is reconstructed.

Estimated turnover left out, box 55 ticked

Turnover entered: £65,500
Profit taxed: £23,000
Tax at 19%: £4,370

Best estimate included, box 55 ticked

Turnover entered: £72,000
Profit taxed: £29,500
Tax at 19%: £5,605

What box 55 changes

Ticking box 55 does not alter turnover, stock, profit or Corporation Tax. We file the numbers you enter and add the estimated-figures declaration to the Corporation Tax return sent to HMRC. The company remains responsible for the figures and for the existing declaration that the return is correct and complete to the best of its knowledge and belief.

Worked example

Company: Juniper Example Ltd
Accounts period: 1 July 2024 to 30 June 2025 (12 months)
Final figures: Raw materials £12,000, staff costs £21,000, other charges £9,500
Estimated figure: Turnover £72,000, of which £6,500 is reconstructed from bank deposits because some sales records were lost
Final figure expected: When the payment provider sends its statements

The company and all figures on this page are fictional.

Before you start

Which figures are estimates: And the field each one goes in. The estimate goes in the normal field for that figure.
How each estimate was made: Keep the working. How the estimate is made is for you or your accountant to decide.
When final figures are expected: If you know. If not, be ready to say why.
For two CT600s: Which return each estimate belongs to, if that matters.

The company and all figures on this page are fictional.

Step by step

Company Profile & Period
Set up the filing as normal.
Accounting period
1 July 2024 to 30 June 2025
What are you filing?
HMRC CT600 or Companies House & HMRC CT600Which to choose
Trading status
ActiveThe form starts on Dormant, so make sure you change it.
What the company does
TradingRequired before you continue. Choose the kind of business the company carried on.
Complete the other choices on the screen and click Next →.
Financial Data
Enter each figure in its normal field, including the estimate.
Previous year
Last year’s figures, from your previous accountsRequired before you continue. Figures from Companies House fill in where available. Check them, and enter 0 where a line had no amount.
Turnover
72000Includes the £6,500 estimate
Cost of raw materials and consumables
12000
Staff costs
21000
Other charges
9500
Balance sheet
Your balance sheet at the end of the period
Average number of employees
Your average number, or 0
This Corporation Tax return contains estimated figures
Tick itAt the bottom of the page, after Employees. With File only the remaining CT600 there is no Employees section, and it is still at the bottom.
Explanation of estimated figures
Turnover includes £6,500 reconstructed from bank deposits because some sales records were lost. The final figure is expected when the payment provider sends its statements.
Click Next →.
Review & file
The Corporation tax due card is the same as it would be without the tick. For Juniper Example Ltd:
Corporation tax due
£5,605 .00
On taxable total profits of £29,500 at 19.0% · small profits
Check the documents
Click Preview your documents (free)Box 55 on the Company Tax Return PDF shows an X, and the tax computation includes your explanation.
Subscribe
Click Unlock Filing and complete payment
Continue
Click Continue to submission
More help: PDF copies of your filing documents
Filing credentials
Corporation Tax UTR
Your 10-digit UTR
Gateway User ID
Your Government Gateway user ID
Gateway Password
Your Government Gateway password
Select the director submitting this return
The director’s name
Accounts approval date
The date the directors approved the accountsWhat to enter
Declaration
Tick it
Click Submit to HMRC, or Submit to HMRC & Companies House.
After you submit
The return shows Accepted under Gateway submissions once HMRC confirms it. HMRC usually replies within a few minutes, but it can take longer.

A long accounting period can produce two Corporation Tax returns. We apply the same box 55 answer to both returns and include the same explanation in both computations. Say which return an estimate relates to where that matters. You can read more about the PDF copies of your filing documents and how the official-form PDF reflects the XML sent to HMRC.

When final figures become available

Compare the final figure with the estimate and decide whether the filed return needs correcting. If it does, file an amendment within the applicable time limit. HMRC says you must usually make changes within 12 months of the filing deadline. Our guide explains how to amend a CT600. On the amended return, leave box 55 selected only if that replacement return still contains an estimated figure.

More help: GOV.UK: making changes to a Company Tax Return

This article is general guidance, not tax or accounting advice. If you are unsure whether a figure is a reasonable estimate or whether an amendment is needed, ask an accountant.

Sample outcome

Box 55 marked XOn the CT600 sent to HMRC, and on both CT600s for a long period

£5,605Corporation Tax on £29,500 at 19%. The same with or without the tick

Explanation attachedIn the tax computation, not in a separate letter

Not the right guide?

Open the guide that matches your situation.

How to amend a CT600Replace a filed return once final figures are known.What are you filing?HMRC CT600, Companies House or both.Several years behindOne filing per period, oldest first.

Looking for a different field or step? See all filing wizard guides →

Official sources

Whether this route matches your filings is for you to decide, yourself or with your accountant.

Example companies and figures are fictional. Field names match the filing wizard as of 12 October 2026.