Guides
CT600 vs Making Tax Digital
A clear comparison: the annual CT600 corporation tax return versus the quarterly Making Tax Digital regime — what each is, who has to do it, and how they relate.
Quick answers
Do I file Corporation Tax quarterly under MTD?
No. Corporation Tax is filed annually on the CT600 with iXBRL accounts and computation. MTD for Corporation Tax is not currently mandated.
What does MTD actually cover?
MTD VAT (mandatory now) and MTD for Income Tax for sole traders and landlords (phasing in from April 2026).
CT600 vs Making Tax Digital
Directors of small companies often think Making Tax Digital (MTD) means they must file Corporation Tax quarterly. It does not. The CT600 and MTD are two different regimes, and only one applies to Corporation Tax today.
What is the CT600?
The CT600 is the company tax return. Every active UK company files one for each accounting period.
- Submitted online to HMRC's Corporation Tax service.
- Accompanied by iXBRL accounts and an iXBRL tax computation.
- Due 12 months after the accounting period end.
- Tax payable 9 months and 1 day after the period end (instalments above £1.5m profits, adjusted for associated companies).
The CT600 is annual. There is no quarterly equivalent.
What is Making Tax Digital?
MTD is a programme that requires digital record keeping and digital submissions for specific taxes:
- MTD VAT — live since 2019; mandatory for all VAT-registered businesses.
- MTD for Income Tax (MTD ITSA) — phasing in from April 2026 for sole traders and landlords above income thresholds.
- MTD for Corporation Tax — paused; no mandatory start date.
So MTD is real and growing, but it does not yet cover Corporation Tax.
Side-by-side
| CT600 | MTD VAT | MTD ITSA | |
|---|---|---|---|
| Who | UK companies | VAT-registered businesses (incl. companies) | Sole traders & landlords above threshold |
| Frequency | Annual | Quarterly (or monthly) | Quarterly + final declaration |
| Format | iXBRL via HMRC CT online | Digital links via MTD API | Digital records via MTD API |
| Replaces | Nothing — it's the CT return | Old VAT100 portal | Self Assessment for ITSA filers |
Why the confusion
- HMRC has consulted on MTD for Corporation Tax for years, so the topic comes up in news headlines without being mandatory.
- Companies that are VAT registered already use MTD VAT, so it feels like "the company is in MTD" — which is true for VAT only.
- Directors of one-person companies are often also self-employed or landlords personally, where MTD ITSA does apply.
What this means for a small Ltd company
You should:
- File one annual CT600 with iXBRL accounts and computation. See Corporation Tax explained and the worked CT calculation.
- If VAT registered, run MTD VAT quarterly with digital links end-to-end.
- Personally, check whether MTD ITSA applies to you from April 2026 onwards based on your personal property and self-employment income.
For the company-only view see Limited companies and Making Tax Digital.
Frequently asked questions
Related guides
Corporation Tax Explained: Rates, Computation and CT600 Filing
How Corporation Tax works for UK limited companies in 2025/26 — rates, marginal relief, what to deduct, and how to file your CT600.
Example: Corporation Tax Calculation with Marginal Relief
A worked example of a UK Corporation Tax calculation for 2025/26 showing taxable profit, marginal relief and the final tax due.
Limited Companies and Making Tax Digital
What MTD does and does not cover for UK limited companies in 2025/26 — MTD VAT today, MTD for Corporation Tax in the future.
Making Tax Digital (MTD) Explained
What MTD means for VAT and Income Tax, who's affected, when the rules apply, and how to choose compatible software.