UK CT600 & Company Tax Return Filing Service

Tax Services

Company Tax Return & CT600 Filing
Prepared for HMRC

A company must submit a Company Tax Return when HMRC issues a notice to deliver, including for relevant active periods. After HMRC records a company as dormant for Corporation Tax, no further Company Tax Return is normally required unless HMRC asks. Accusolve prepares returns that are due and helps companies manage the applicable deadlines and reliefs.

Accusolve is an AAT AML-supervised UK accountancy practice supporting startups, SMEs and overseas directors of UK companies. We prepare the Company Tax Return package, explain the calculations and submit agreed filings using suitable software.

What the Company Tax Return Includes

The CT600 is one part of the filing package. Depending on your company and accounting period, the return includes:

The CT600 and applicable supplementary pages
Company accounts and Corporation Tax computations
Appropriate iXBRL accounts and computation content where required
Relevant supporting information for claims within the agreed scope

We review expenses and applicable allowances. Capital allowances, group relief, R&D claims and other specialist reliefs are considered only where relevant, supported by evidence and included in our agreed work. Companies House annual accounts filing remains a separate obligation.

Company Tax Return Filing After March 2026

HMRC's former free joint online filing service closed on 31 March 2026. Company Tax Returns now generally require suitable commercial filing software, with limited paper-return circumstances such as filing in Welsh or having a reasonable excuse. We prepare and file returns through appropriate professional software; see HMRC's guidance on the service closure. Our guide to CT600 filing after March 2026 explains the software change and what companies need to prepare.

Company Tax Return vs Corporation Tax Payment Deadlines

The return is normally due 12 months after the end of the Corporation Tax accounting period. Payment is normally due 9 months and 1 day after that period for companies outside instalment-payment rules, so payment can fall before the filing deadline. We review the relevant periods and explain your Corporation Tax obligations.

First accounts or accounts covering more than 12 months can require more than one tax return because a Corporation Tax accounting period cannot exceed 12 months. Check the applicable periods rather than assuming one accounts deadline covers every return and payment. See GOV.UK Company Tax Return guidance.

How the CT600 Filing Process Works

Review the company status, HMRC notices, accounting periods and outstanding deadlines.
Gather accounts and records, resolve queries and prepare the tax computation and return package.
Explain the draft figures, reliefs and payment position for your review and approval.
Submit the agreed return and provide the filing acknowledgement and next steps.

If the company is not trading, we review HMRC's status and any notices before deciding what is required. Our dormant company accounts support explains the separate Companies House and HMRC obligations.

What We Need From You

Company number, UTR, HMRC notices and previous returns
Accounts or bookkeeping records, bank statements and reconciliations
Sales, expenses, payroll, assets, loans and director balances
Details of losses, associated companies and any proposed relief claims

We agree the records and authorisation needed for your circumstances and flag missing information that may affect preparation or submission.

CT600 Tax Return FAQ's

What is a CT600 tax return?

A CT600 forms part of the Company Tax Return a company must submit when HMRC issues a notice to deliver, including for relevant active periods. After HMRC records a company as dormant for Corporation Tax, no further Company Tax Return is normally required unless HMRC asks.
When is the CT600 filing deadline?

The return is normally due 12 months after the Corporation Tax accounting period ends. Payment is normally due 9 months and 1 day after the period for companies outside instalment-payment rules, before the filing deadline. Long or first accounts may involve more than one tax return.
What happens if I file my CT600 late?

Late filing can lead to HMRC penalties. We can review outstanding returns and notices, explain the position and agree a preparation timetable based on the records available.
Can Accusolve help overseas company directors with CT600 returns?

We help UK-based and overseas directors with UK company returns. We review the company circumstances and agree the scope, including any residence or cross-border questions requiring separate advice.

Switch accountants with a smooth handover for accounts, tax records and new accounting support

Need Help Filing Your CT600?

Discuss your accounts, HMRC notices and filing deadlines with our UK accountancy and tax team. We can prepare the required return package and explain the next steps.

Discuss Your CT600 Filing

Professional CT600 Tax Return Support