BillingEngine MCP server

Create customers and invoices, look up open invoices and record payments in BillingEngine by talking to Claude, Cursor or any other MCP client:

"Create an invoice for Acme Painting over 100 euros."

"Which invoices are overdue?"

"Acme paid invoice 2610030028, record the payment."

BillingEngine is invoicing software for freelancers and small businesses with e-invoicing (EN 16931, XRechnung, ZUGFeRD / Factur-X). The server is a thin layer over the BillingEngine API and runs on your computer.

Requirements

• Node.js 20 or newer
• A BillingEngine account on a paid plan. The API is not available in the Free plan.
• Your API key from Settings > API keys in BillingEngine

Setup

Claude Desktop

Add this to claude_desktop_config.json:

{
  "mcpServers": {
    "billingengine": {
      "command": "npx",
      "args": ["-y", "billingengine-mcp"],
      "env": { "BILLINGENGINE_API_KEY": "your-api-key" }
    }
  }
}

Claude Code

claude mcp add billingengine --env BILLINGENGINE_API_KEY=your-api-key -- npx -y billingengine-mcp

Cursor and other clients

Use the same command, args and env as above in the MCP settings of your client.

Tools

What it does and does not do

• Invoices are created as drafts. Nothing is sent to your customers; you review and send the invoice in BillingEngine. Every result contains a link to open the draft.
• Prices are net or gross, as set in your account; every invoice says which. Amounts in results are decimal strings such as "119.00". Number, language, texts, VAT treatment and payment terms come from your account settings, exactly as in the invoice form.
• Nothing can be deleted through this server.
• New invoices count towards the monthly invoice maximum of your plan.
• The API allows 60 requests per minute per key.
• Your key stays on your computer and is only sent to BillingEngine.

If a key is ever exposed, create a new one under Settings > API keys. The old key stops working immediately. The settings also show when the key was last used.

Configuration

Development

npm install
npm run build
BILLINGENGINE_API_KEY=... node dist/index.js

License

MIT. BillingEngine itself is a commercial service; see billingengine.com.