Fylix API Reference
Build powerful tax compliance integrations with our RESTful API. Automate tax filing, sync financial data, and manage clients programmatically.
API Overview
Our REST API is designed for developers who want to integrate Fylix into their applications.
OAuth 2.0 Authentication
Secure authentication flow with access tokens and refresh tokens for long-lived integrations.
Rate Limiting
Fair usage with 1000 requests per hour per API key. Enterprise plans available for higher limits.
Webhooks
Real-time notifications for tax return status changes, submission confirmations, and more.
Base URL
All API requests should be made to this base URL with the appropriate endpoint path.
Authentication
Include your API key in the Authorization header for all requests.
Available Endpoints
Comprehensive REST API covering all aspects of tax management and compliance.
Tax Returns
Create, update, and submit self-assessment tax returns programmatically.
Transactions
Import, categorise, and manage income and expense transactions.
Properties
Manage rental properties and associated income records.
Clients
Client management endpoints for accountancy practices.
Reports
Generate tax reports, analytics, and export financial data.
Quick Start Example
Get started with a simple API call to fetch tax return data.
# Example: Fetch tax return summary
curl -X GET https://api.fylix.co.uk/v1/tax-returns/2025 \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json"
# Response
{
"id": "tr_abc123",
"tax_year": "2024-25",
"status": "submitted",
"total_income": 75000.00,
"total_expenses": 12500.00,
"tax_liability": 15750.00,
"submitted_at": "2026-01-31T23:59:00Z"
}Rate Limits
Free: 100 requests/hour
Professional: 1,000 requests/hour
Enterprise: 10,000+ requests/hour
Rate limits are applied per API key. Contact us for custom limits.