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.
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Plain-English guides to UK Corporation Tax and CT600 filing.
Limited Company Director Salary 2025-26 — The Optimal Amount to Pay Yourself
What salary should a limited company director take in 2025-26? We break down the optimal salary level to minimise tax, including NI thresholds and corporation tax impact.
Company Year End: 31 March vs Other Dates — How It Affects Your CT600
Does your company year end matter for corporation tax? Yes. Here's how 31 March simplifies your CT600 filing, and what happens with other year-end dates.
CT600 Capital Allowances — AIA, Full Expensing, and Writing Down Allowances Explained
Complete guide to claiming capital allowances on your CT600. Covers Annual Investment Allowance (AIA), full expensing, writing down allowances, and which boxes to fill in.
Capital Allowances on Your CT600 — AIA, WDA, and Full Expensing Explained
How to claim capital allowances on your CT600 for equipment, vehicles, and machinery. Covers AIA, writing down allowances, full expensing, and which CT600 boxes to use.
CT600 Box by Box — Which Boxes Do I Actually Need to Fill In?
The CT600 has 200+ boxes but most companies only need about 30. Here's exactly which boxes matter for your company type — micro-entity, small, or dormant.
CT600 Penalties for Late Filing — What Happens If You Miss the Deadline
HMRC charges escalating penalties for late CT600 filing, starting at £100. Here's exactly what happens, how to avoid penalties, and what to do if you've already missed the deadline.
CT600 Marginal Relief Explained — How to Calculate Corporation Tax 2024-25
Marginal relief reduces corporation tax for companies with profits between £50,000 and £250,000. Learn how it works, how to calculate it, and how it appears on your CT600.
Dormant Company CT600 — How to File a Nil Return
Your dormant company still needs to file a CT600 with HMRC. Here's how to file a nil return quickly and avoid penalties — even if your company did nothing all year.
CT600 Filing for First-Time Directors — Complete Beginner Guide
New company director? This beginner-friendly guide explains CT600 corporation tax returns: what they are, when to file, what you need, and how to do it yourself.
How to File CT600 Online After HMRC Free Service Closes
Step-by-step guide to filing your CT600 corporation tax return online using commercial software after HMRC discontinues its free filing service in March 2026.
CT600 Box-by-Box Guide for Small Companies (2025/26)
Plain English explanation of every CT600 box that matters for a typical small limited company. No jargon, no confusion.