How Your CT600 Is Submitted to HMRC — Format and Verification
TinyTax only supports accounts filed in GBP (sterling). When you preview your CT600 in TinyTax, you can download it as a PDF. This guide explains what format the CT600 is submitted in and how to verify your figures before submitting.
CT600 Format: XML, Not iXBRL
The CT600 corporation tax return is submitted to HMRC as an XML file using HMRC's proprietary CT600 schema. This is different from your statutory accounts and tax computation, which are submitted in iXBRL (inline XBRL) — a tagged HTML format that opens in a web browser.
| Document | Format submitted to HMRC | Preview available |
|---|---|---|
| CT600 (corporation tax return) | XML | PDF only |
| Statutory accounts | iXBRL (HTML) | HTML and PDF |
| Tax computation | iXBRL (HTML) | HTML and PDF |
How to Verify Your CT600
The CT600 PDF is the authoritative way to review your return before submitting. It shows:
- All CT600 box numbers and their values
- Your taxable profit and corporation tax liability
- Any reliefs, losses, or adjustments applied
The PDF and XML Use the Same Figures
The CT600 PDF and the XML file sent to HMRC are generated from the same underlying data. The XML includes additional metadata and schema formatting required by HMRC's submission system, but the monetary values are identical.
Common Questions
Why can I preview the accounts in iXBRL but not the CT600?
Accounts use the iXBRL format because Companies House and HMRC require structured data tags embedded in the document. The CT600 uses a separate XML schema defined by HMRC, which is not iXBRL.
If the PDF looks correct, can I be confident the submission will be accurate?
Yes. The PDF and the XML submission are generated from the same figures. A correct PDF means a correct submission.
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