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DO-IT-YOURSELF CT600

Self-service corporation tax filing for limited companies

Prepare your own figures, choose the accounts regime that applies and submit your Company Tax Return using software. Understand your legal responsibilities first, then use the checklist to keep the records and separate deadlines in view.

Start your CT600 filing Compliance checklist

01 / YOUR FILING, YOUR RESPONSIBILITY

What self-service filing means

Self-service means you prepare your company's figures and submit its CT600 Version 3 return and applicable accounts using software, rather than instructing an accountant to prepare them for you. Whether you file yourself or appoint an accountant, the director remains legally responsible for accurate and timely filings.

It can suit a straightforward micro-entity with reliable records or a dormant company with filing obligations. Complex group affairs, R&D claims requiring CT600L, or other unsupported supplementary pages may need different software or professional help. WeFile does not support CT600B–D or CT600F–P. WeFile provides no tax advice.

02 / KEEP THE OBLIGATIONS SEPARATE

Legal requirements for a micro-entity

If HMRC has issued a notice to deliver a Company Tax Return and has not withdrawn it, the company must file a CT600. An online return normally includes iXBRL accounts and a tax computation. Paper returns are allowed only in limited circumstances. Statutory accounts are a separate filing to Companies House, including for companies that qualify to file dormant accounts.

9 months + 1 dayCorporation Tax is normally payable by this point after the accounting period ends, outside the instalment-payment regime.
12 monthsThe CT600 is normally due 12 months after its Corporation Tax accounting period ends.
9 monthsA private company's annual accounts are normally due nine months after its accounting reference date. First accounts generally have a different deadline.
6 yearsKeep company accounting records for six years from the end of the financial year they relate to, or longer where a relevant exception applies.

For CT600 returns with a filing date on or after 1 April 2026, the fixed late-filing penalties are £200 when late and a further £200 when more than three months late (£400 overall). After three successive late returns, they rise to £1,000 and a further £1,000 (£2,000 overall). Other HMRC penalties and separate Companies House late-accounts penalties may also apply.

HMRC's free joint online filing service closed on 31 March 2026. Read what changed when the free CT600 filing service closed.

Sources: GOV.UK Company Tax Returns, GOV.UK annual accounts, GOV.UK CT600 penalty increase, and GOV.UK company records.

03 / MATCH THE ROUTE TO THE WORK

Self-service vs an accountant: cost vs complexity

Software gives you a filing workflow; an accountant can provide preparation and advice within their agreed scope. Compare the complexity of your company's affairs, not just the filing price.

Which filing route fits your circumstances?WeFile per filing:
Company situationSelf-service with WeFileConsider an accountant when…
Dormant companyDormant accounts are supported. File a CT600 if an HMRC notice to deliver remains in force.You are unsure whether the company was dormant or what HMRC requires.
Simple micro-entity, single director, clean booksEnter or import figures, reconcile them and review the generated return and accounts.Records are incomplete or you need accounting or tax advice.
Small company with director loansWeFile supports CT600A for applicable close-company loans to participators.The loan history or tax and repayment treatment is uncertain.
Charity or CASCSupported CT600E returns are CT600-only. WeFile does not file charity or CASC accounts with Companies House.You need help establishing exemptions, taxable income or separate accounts obligations.
Group company, R&D or overseas incomeCheck the required pages and calculations first. CT600B–D and CT600F–P are unsupported.Reliefs, cross-border treatment or unsupported pages require specialist work.

For a fuller decision guide, see filing yourself versus using an accountant. No software workflow replaces professional advice.

04 / CHOOSE THE ACCOUNTS REGIME

How the wizard handles FRS 105 and FRS 102

At the account-type step, you select micro-entity accounts under FRS 105 or supported small-company full accounts under FRS 102 Section 1A. WeFile formats the generated accounts accordingly and tags supported accounts for iXBRL submission. FRS 105 presents a collapsed balance sheet; the supported FRS 102 presentation shows separate items such as intangible assets.

FRS 105 does not permit fair value accounting. Relevant fair value lines are therefore available only in the supported FRS 102 accounts. You remain responsible for deciding which regime applies and reviewing the resulting documents.

Check the FRS 105 eligibility indicator before choosing. You can also compare micro-entity accounts and small-company accounts.

05 / FROM RECORDS TO SUBMISSION

Five steps to self-file

  1. Add your company and confirm the accounting period

    Check the company details and period dates against your records and any HMRC notice to deliver a Company Tax Return.

  2. Enter or import your profit and loss figures

    Enter your figures or import bookkeeping data from Xero, QuickBooks Online, FreeAgent or CSV, then review the result.

  3. Complete the balance sheet and capital allowances

    Enter assets, liabilities and qualifying expenditure. Your profit and loss account and balance sheet must reconcile.

  4. Review the tax calculation and generated accounts

    Check the automatically calculated Corporation Tax and the accounts generated under your selected FRS 105 or FRS 102 regime.

  5. Submit to HMRC and, where applicable, Companies House

    Submit the CT600 Version 3 return with your Corporation Tax-enrolled Government Gateway credentials. Submit eligible accounts separately with your Companies House authentication code and track each result.

06 / TWO DESTINATIONS, TWO RESULTS

Direct submission to HMRC and Companies House

WeFile sends supported filings electronically to each authority and shows their submission statuses separately. WeFile appears on HMRC's Corporation Tax commercial software suppliers list; inclusion on that list is not an endorsement or recommendation.

HMRC return

Submit the CT600 to HMRC's Transaction Engine using your Corporation Tax-enrolled Government Gateway credentials.

Companies House accounts

Where applicable, submit accounts through its software filing service using your Companies House authentication code.

Checks and tracking

Pre-submission reconciliation checks help identify problems. Track results in the app; an IRmark is shown when HMRC supplies one.

Protected credentials

Government Gateway passwords and Companies House authentication codes are encrypted at rest.

Checks reduce common errors but cannot guarantee acceptance. See how CT600 submission and status tracking work.

07 / REVIEW BEFORE YOU SEND

Common self-filing pitfalls

Period datesA CT600 period cannot exceed 12 months. Check whether a longer accounts period needs two Corporation Tax returns.
Company identifiersCheck the UTR and company details against HMRC's records.
Tax adjustmentsReview disallowable expenses such as accounting depreciation and client entertaining; distinguish them from capital allowances.
Additional disclosuresCheck whether director loans require CT600A and whether associated companies affect the tax calculation.
Access and deadlinesConfirm Government Gateway Corporation Tax enrolment and note that the normal tax payment deadline comes before the CT600 filing deadline.

See the fuller CT600 mistakes checklist and the guide to HMRC submission errors. Investigate any reported rejection before resubmitting.

QUESTIONS, ANSWERED

Self-service Corporation Tax filing FAQs

Yes. A director can prepare and file a CT600 Version 3 return using suitable software if the company’s circumstances are supported. The director remains responsible for the return’s accuracy, completeness and deadline. Seek qualified advice when the company’s affairs are complex or uncertain.
If HMRC has issued and not withdrawn a notice to deliver, the company must file a CT600, normally with iXBRL accounts and a tax computation for an online return. Annual accounts are filed separately with Companies House. Corporation Tax is normally payable nine months and one day after period end, the CT600 is normally due within 12 months, and private-company accounts are normally due nine months after the accounting reference date. Applicable exceptions and first-accounts deadlines should be checked.
With self-service software, you prepare and review the figures and submit the filings yourself. An accountant may prepare the figures and offer advice within an agreed scope. The director remains legally responsible either way. WeFile is software and does not provide accounting or tax advice.
Prepare the company UTR, Corporation Tax-enrolled Government Gateway credentials, relevant period dates, bookkeeping or trial-balance figures, bank balances and prior-year figures. You may also need asset, director-loan and dividend records. A Companies House accounts submission needs its authentication code.
No. You choose the applicable accounts regime at the account-type step. WeFile formats supported generated accounts for your FRS 105 micro-entity or FRS 102 Section 1A selection, but you must assess eligibility and review the documents.
For supported filings, WeFile sends the CT600 electronically to HMRC using your Corporation Tax-enrolled Government Gateway credentials and, where applicable, submits accounts separately to Companies House using its authentication code. The two submission results are tracked separately; acceptance is not guaranteed.
WeFile shows the reported submission status and error information. Investigate the reason, correct the relevant data or credentials, and resubmit where appropriate. A submission receipt does not guarantee that every later HMRC check has passed.

Ready to file your company's tax return yourself?

Prepare your records, review the calculation and follow each submission separately.

Start your CT600 filing

This guide and checklist provide general information, not professional accounting or tax advice. WeFile is software and does not provide tax advice or replace professional advice. Directors remain responsible for accurate, complete and timely filings and payments. Check the rules that apply to your company and consult a qualified professional where needed.