How to amend a CT600

Amendment, new filing, or re-file: which do I need?

Another period

Start new filing from the company page.

Rejected filing

Use Re-file CT600 or Re-file Accounts on that existing record.

Accepted filing made here

Use Amend this filing. Follow the amendment steps.

Original filed elsewhere

Use Amend filing made elsewhere. Check the company and period in the wizard.

• Amendment is right when a return for this period was already filed and accepted (by us or elsewhere) and you want to correct or update the figures.
• New filing is right when no return has been filed for this period yet. If you try to amend when HMRC has no original on record, you’ll see error 1611.
• Re-file is right when your submission was rejected, because HMRC holds nothing to amend. Fix the problem and submit again as a normal filing. See CT600 filing errors, explained.

Starting another accounting period

You can start another filing while an earlier one is awaiting a response, even if only one authority has accepted it. Select New filing on the company card. If the card shows Resume filing, open its arrow and select Start new filingto leave the saved amendment available for later. You can also select Start new filing on the company page, then choose the accounting period. Resume filing reopens the selected saved filing or amendment instead.

New filing starts with blank dates and figures. Select Resume saved filingto reopen unfinished saved progress instead. Saving the new form replaces unfinished new-filing progress for that company. Saved amendments remain available separately. For more detail, see saving and resuming your filing. To continue correcting a rejected submission, use the company page’s Re-file CT600 or Re-file Accounts action. Your previous filings and re-file work remain available on the company page. To correct an accepted filing, use Amend this filing for that period.

Amending a filing made with SimpleCompanyTax, step by step

This is the simple case. We already hold your original return, so we pre-fill everything.

1. Open the company, then open the accepted filing for the period you need to change and choose Amend this filing.
2. You’ll see a confirmation page first: a read-only summary of what was originally filed and HMRC deadline guidance (see Deadlines). Nothing is created until you proceed.
3. Choose Proceed. We start an amendment pre-filled with your accepted figures and take you to the review page. You’ll see an amber “Amendment” marker throughout, so you always know you’re editing an amendment rather than a new return.
4. Change the figures that need correcting, exactly as you would on an original filing.
5. In the Reason for amendment field, briefly describe what was wrong and why you’re correcting it. This is required and must use 16 to 500 characters. For example: “Capital allowances were understated. A £2,400 equipment purchase was missed.” This is kept with the filing record.
6. Check the destination toggles. Based on what you changed, we pre-select whether the amendment goes to HMRC, to Companies House, or both (see the next section). You can override the defaults. For a return filed elsewhere, File this amendment to starts with your answer to What are you filing? in Company & period. Choose the destinations here. They are shown read-only in Filing credentials. Select at least one destination before continuing. If both are off, your amendment stays saved as a draft and nothing is filed.
7. If Companies House is selected, choose how the accounts should be filed. For Revised accounts or Replace filleted accounts with full accounts, enter Date directors re-approved the revised accounts. Complete this and Reason for amendment before Continue to submission or Preview your documents (free). You can preview without a filing destination.
8. Select Continue to submission. In the dialog, enter the details for the destinations shown and confirm the declaration. To change destinations, close Filing credentials and use File this amendment to on review. We save the authorised amendment details before sending your filing. If that save fails, nothing is sent and you can try again. The final button reads Submit to HMRC, Submit to Companies House or Submit to HMRC & Companies House, according to your choice. If you select HMRC, each previously accepted CT600 is sent as an amended return, rather than a second new return for the same period. If a second CT600 for a long first accounting period has not yet been filed, we send it as a new return. If you select Companies House, we send revised accounts. You can track the outcomes on the filing page.

If you select HMRC for a long first accounting period, check both dated CT600s in the preview before continuing. If the first return was filed and the second has not been filed, follow the first-return amendment and second-return guide.

Amending a CT600 with different accounts and tax dates

SimpleCompanyTax#Simple CompanyTax can amend a divergent-period CT600 that you filed through the service. The amendment keeps both the annual accounts dates and the Corporation Tax dates from the original. You can correct the figures, but you cannot change either date pair inside that amendment. This route files to HMRC only. Any Companies House filing must be arranged separately.

1. Open the accepted filing and choose Amend this filing, then Proceed.
2. Correct the figures and describe the correction in the Reason for amendment field. Keep HMRC as the filing destination.
3. Select Preview your documents (free), then Generate draft preview →. Check the dates and figures in each CT600 and its tax computation.
4. When you are ready, select Continue to submission, complete the declaration and choose Submit to HMRC.

Corporation Tax coverage longer than 12 months regenerates both CT600s as amendments, using the original split dates. Check the saved allocations of capital allowances and other dated amounts between the two returns, and any loss carried from the first return into the second. Each return has its own computation. Attached accounts covering different dates are declared in box 85, or box 80 when the dates match. A second return wholly after the accounts end has no accounts attachment and uses box 90 to say the accounts accompany the separate return. Both returns have box 50 marked.

If the original filing was only the remaining CT600 of a long accounts period, its amendment still contains only that remaining return. The accounts stay omitted because they were supplied with the first return, and the remaining-period computation stays attached.

HMRC, Companies House, or both?

Not every correction affects both regulators, and filing an unnecessary revision creates needless public record changes. We suggest destinations from what actually changed:

• Tax-only changes. Capital allowances, disallowable expenses, brought-forward losses and similar tax adjustments live only in your CT600 and tax computation. Default: HMRC only, because your published accounts are unchanged.
• Balance-sheet-only changes. For example a corrected debtors or creditors figure. Default: Companies House only (revised accounts), because your tax numbers are unchanged.
• Profit & loss changes. Turnover, cost of sales, expenses. These flow into both the accounts and the tax computation. Default: both.

Revised accounts replace the original set on the public register (a “replacement” revision). The revised accounts include the statements required by the Companies (Revision of Defective Accounts and Reports) Regulations 2008, which we add automatically.

Those statements sit on a separate final page headed Revised accounts statement, in the same plain style as the rest of the accounts, and the cover is marked Revised. The page states that the revised accounts replace the original accounts, that they are now the statutory accounts, that they were prepared as at the date of the original accounts, the respects in which the original accounts did not comply and the amendments made, and the date the directors approved the revision. The regulations require these statements in a prominent position, so the page is part of the public filing, but nothing requires a box or a warning. The reason you enter in the Reason for amendment field is printed once, so write it as a short factual description of what was corrected.

Deadlines

• HMRC. By law (Finance Act 1998, Schedule 18, paragraph 15) you can amend a Company Tax Return up to 12 months after the statutory filing deadline. The filing deadline is determined by HMRC's filing-date rules. We show general deadline guidance and do not block submission using a locally calculated deadline. HMRC decides whether it can accept and process your amendment. A gateway receipt alone does not establish that a late amendment has been processed.
• Companies House. Revised accounts have no equivalent deadline. You can file revised accounts even after the HMRC window has closed (the accounts side of the toggle stays available).

Amending a CT600 that was filed elsewhere

For a supported long period, Amend both CT600 returns, Amend the first CT600 and file the second as new and File the first CT600 as new and amend the second can use separate Corporation Tax dates. If the calculated first end differs from HMRC, open Change CT600 split date and edit First CT600 ends. Enter full-period recurring figures once and confirm the capital and event allocations. Amend only the second CT600 uses First CT600 ends to set the remaining start, and takes remaining-period figures only. Follow the date-matching steps for each route.

The Filing purpose cards show which returns will be amended or filed as new. Open the help icon on a card for details about figures and accounts. To correct only the second CT600 of a long accounts period, choose Amend only the second CT600 under Filing purpose. Enter the full accounts dates and corrected figures for the remaining period only. Follow the second-return amendment guide.

If the original return was filed another way, you can still prepare the amendment here. Start from the company already on your dashboard.

1. Open your company and select Amend filing made elsewhere.
2. In Company & period, check the company details and registered office. You can edit the office here.
3. Choose the accounting period you are amending from the Companies House list. Filed periods are marked Accounts filed. Choose Custom dates if the period is not listed.
4. Choose What are you filing? in Company & period, then complete the return with your corrected figures. On Review & file, File this amendment to starts with that answer. Choose the destinations here. They are shown read-only in Filing credentials. If both are off, your amendment stays saved as a draft and nothing is filed.
5. Enter Reason for amendment, using 16 to 500 characters to describe the correction. If Companies House is selected, choose the filing kind. For Revised accounts or Replace filleted accounts with full accounts, enter Date directors re-approved the revised accounts. These are required before Continue to submission or Preview your documents (free). A preview can have no filing destination.

If Companies House has no accounting dates for the company, you are asked for Period start and Period end first. Enter the period you are amending and select Continue.

An unincorporated club enters its period because there is no Companies House list. Follow the club amendment steps for the HMRC-only route.

Check these details against the original return before filing:

• UTR (Unique Taxpayer Reference): the 10-digit company tax reference HMRC holds for this company.
• Accounting period start and end dates: they must match the dates of the return HMRC already has, to the day.

If either doesn’t match, HMRC can’t find the original and returns error 1611 (“no original return found”). Double-check the UTR and the exact period dates against your HMRC online account or the original return, then resubmit. If they’re correct and it still fails, call the HMRC Online Services Helpdesk on 0300 200 3600.

Official amendment guidance

HMRC explains online amended returns and processing, the amendment notice and time limits, and CT600 dates, accounts and computations. An electronic receipt does not by itself establish that HMRC has processed an amendment on its company record.

What it costs

Amendments and revised accounts are included free for each paid year. Prepare corrections as needed. HMRC determines whether an amendment can be accepted. Without an active subscription, amending works like any other filing: subscribe first, then amend.

This article is general guidance, not tax advice. If you’re unsure whether a correction is needed, for example whether an error is material enough to revise your accounts, speak to an accountant.

If only the second CT600 has been filed and the first is still outstanding, file the first CT600 as new and amend the second. That route sends both returns and includes the full accounts, rather than leaving the first unchanged.