CT600 Box by Box — The Most Important Boxes Explained
The CT600 has over 200 boxes but most companies only use a fraction. Here are the key boxes you need to know, what goes in each one, and common mistakes to avoid.
Plain-English guides to UK Corporation Tax and CT600 filing.
The CT600 has over 200 boxes but most companies only use a fraction. Here are the key boxes you need to know, what goes in each one, and common mistakes to avoid.
The most common CT600 filing mistakes that cause HMRC rejections. Learn what to avoid so your Corporation Tax return gets accepted first time.
How to claim Annual Investment Allowance on your CT600. £1 million limit, qualifying assets, how to calculate, and common mistakes.
Comprehensive CT600 box-by-box guide for 2025/26. What goes in each box, common mistakes, and worked examples for every section of the Corporation Tax return.
What happens to your Corporation Tax obligations when closing a limited company. Final CT600 filing, strike-off timing, and common mistakes to avoid.
Made an error on your CT600? Learn exactly how to amend your corporation tax return, HMRC time limits, penalties for mistakes, and how to fix common CT600 errors step by step.
A plain English guide to the CT600 boxes that matter for small companies. Learn which boxes to fill in, which to skip, and how to avoid common mistakes.
HMRC's free filing service closes March 2026. Here's exactly how to file your CT600 corporation tax return online in 2026 — step by step, with tips and common mistakes to avoid.
Box 155 is the most important number on your CT600. Learn exactly what trading profits means, how to calculate it, and common mistakes to avoid.
Filing your own CT600? Avoid these 12 costly mistakes that catch first-time filers. From wrong accounting periods to missed reliefs — save time and tax.
Made an error on your CT600? Learn how to amend your corporation tax return within the 12-month deadline, what changes HMRC allows, and the step-by-step process.
New limited company? Learn when to register for corporation tax, your first accounting period, filing deadlines, and how to avoid common first-year mistakes.