Documentation

Getting Started

OpenCT is an AI-native Corporation Tax filing platform for UK SMEs. File your CT600, SA100, and VAT returns with HMRC directly from your browser.

1. Create Your Company

After registering, create a company profile with your Companies House number, UTR, and accounting period dates. We auto-populate details from Companies House where possible.

2. Import Your Books

Upload a trial balance CSV from Sage 50, Sage Business Cloud, Xero, QuickBooks Online, FreeAgent, or any generic CSV. Our AI classifier maps your nominal codes automatically.

3. Review & Adjust

Review the auto-generated P&L and Balance Sheet. Add year-end adjustments (depreciation, accruals, prepayments, bad debts) or let the auto-depreciation engine calculate them.

4. Compute & Validate

Run the corporation tax computation engine. The platform calculates trading profits, capital allowances, marginal relief, and maps every figure to the correct CT600 box. Full BVR, XML, and iXBRL validation runs automatically.

5. Submit to HMRC

Once the director signs off, submit your CT600 and iXBRL accounts directly to HMRC via the Government Gateway. Track submission status in real time.

API Documentation

For developers and integration partners, our REST API documentation is available at /api-docs (Swagger UI).

Support

Need help? Contact us at support@openli.ai or use the AI assistant within the platform.