User & Developer Guides

📖 Part 1: General User Guide

Agent Invoice is a premium, Apple-inspired invoicing platform designed for freelancers, boutique agencies, and developers to manage clients, issue beautiful custom invoices, and collect payments frictionlessly.

Our core goal is to remove administrative friction. By providing a clean interface, secure Stripe/PayPal integrations, and advanced automation out-of-the-box, we let you focus on your work instead of collecting payments.

1. Invoicing Workflow

Agent Invoice operates on a simple, structured billing lifecycle:

1. Add a Client: Head to the Clients tab and click New Client. Provide their company name, email, phone, and billing address.
2. Create an Invoice: Go to the Invoices tab, click New Invoice, select your client from the instant auto-complete dropdown, select a due date, and add line items. Subtotals, taxes, and totals are computed dynamically.
3. Send & Collect Payments:
   • Click Download PDF to obtain a pixel-perfect offline copy.
   • Click Send Invoice to dispatch a high-deliverability email containing the PDF and a secure Stripe Checkout / PayPal wallet payment link.
   • Or click Copy Client Link to get a shareable URL you can text or paste into any chat. Your client opens the invoice in their browser and pays there - no account needed, and nothing to get caught by a spam filter. The invoice detail view tells you whether the link has been opened.
   • Once a payment is collected, the invoice is automatically marked as Paid, and an outbound webhook is fired to trigger any connected integrations!
   • Taking a deposit? Record any payment against an invoice - bank transfer, cheque, cash, whatever arrived - and it becomes Partly paid with the balance tracked for you. Your client sees what they have paid and what is left, reminders chase only the outstanding amount, and the invoice flips to Paid by itself once the balance reaches zero.

2. Settings & Billing Management

• Business Logo: Available on every plan, including Free. Upload a clean rectangular image to sync automatically onto your client invoices and outgoing email headers.
• Templates & Branding: The Presets & Custom Templates tab (available on every plan) lets you choose from built-in presets like Modern Blue, Classic Serif, Minimal Clean, and others, and set your own primary/secondary brand accent colors. The AI Design Studio tab (Pro & Agency Pro) lets you describe your brand in a text prompt to generate a custom AI invoice design, or manually fine-tune fonts, colors, watermarks, and background patterns. Saving custom designs requires Pro or Agency Pro.
• Custom SMTP Sending Domain: (Pro & Agency Pro) Send invoice emails from your own domain instead of our shared delivery servers.
• Payment Methods: Stripe and PayPal are available on every plan. Check and Bank Transfer/ACH payment instructions require Starter or higher.
• Automated Email Reminders: (Pro & Agency Pro) Automatically follow up with clients as an invoice approaches or passes its due date.
• USPS Mail Delivery: Physically mail invoices via USPS (US only) - pay-as-you-go on Starter, 3 free mailings/month on Pro, 10 free mailings/month on Agency Pro, with additional credits purchasable anytime.
• Dedicated Billing Dashboard: Access your billing history, check your monthly invoice usage, download past receipts, update active payment cards, or switch subscription billing cycles (Monthly to Annual to instantly save ~20%) seamlessly via the secure Stripe Customer Portal.

💻 Part 2: Developer API Reference

For developers, boutique agencies, and AI coding agents (such as Claude Code, Open Claw, etc.), Agent Invoice exposes a fully secured programmatic REST API.

Authentication

Developer API access, including key generation and outbound webhooks, is available exclusively on the Agency Pro plan. To authenticate incoming requests, generate a secure Secret API Key under Settings → Developer API. All authenticated requests must pass this key as a Bearer token in the Authorization header:

Authorization: Bearer ie_live_your_secret_key_here

3. Invoices API Endpoints

All API endpoints reside under the base path /api.

[
  {
    "id": "e98e4d29-c189-43c2-bf7f-442478d1f2a3",
    "invoice_number": "INV-1001",
    "client_name": "Acme Corp",
    "total": 105.00,
    "status": "paid",
    "due_date": "2026-06-30T00:00:00.000Z",
    "created_at": "2026-05-31T03:46:28.000Z"
  }
]

// REQUEST BODY
{
  "client_id": "4ac01bb6-fc9c-49f8-b3d2-c2de52d6a111",
  "due_date": "2026-06-30",
  "notes": "Thank you for your business!",
  "tax_rate": 8.25,
  "line_items": [
    {
      "description": "Premium Consultation Services",
      "quantity": 2,
      "unit_price": 50.00
    }
  ]
}

4. Clients API Endpoints

// REQUEST BODY
{
  "name": "Alex Mercer",
  "email": "alex@mercer.com",
  "company": "Mercer Industries",
  "phone": "+1 (555) 765-4321",
  "address": "789 Broadway, New York, NY 10003"
}

5. Outbound Webhooks (Agency Pro)

Whenever important events take place in Agent Invoice, the system dispatches a POST webhook to your configured Webhook Endpoint URL. This feature is available on the Agency Pro plan and requires a Webhook Endpoint URL to be saved under Settings → Developer API.

Supported Event Triggers

• invoice.created - Dispatched when a new invoice is created.
• invoice.sent - Dispatched when an invoice notification email is sent to the client.
• invoice.paid - Dispatched when an invoice is marked paid, online or manually.

Webhook Payload Structure

{
  "event": "invoice.paid",
  "timestamp": "2026-05-31T03:46:28.000Z",
  "data": {
    "id": "e98e4d29-c189-43c2-bf7f-442478d1f2a3",
    "invoice_number": "INV-1001",
    "client_name": "Acme Corp",
    "client_email": "billing@acme.com",
    "total": 105.00,
    "currency": "USD",
    "status": "paid",
    "due_date": "2026-06-30T00:00:00.000Z"
  }
}

Connecting to n8n, Zapier, Make, or Any Automation Tool

Agent Invoice does not publish a dedicated n8n node or Zapier/Make app - it sends a plain webhook that works with any tool capable of receiving one:

1. Generate a receiving URL: Inside your automation workspace (e.g., n8n's Webhook trigger node, Zapier's "Catch Hook" trigger, or a Make Webhook module), copy the unique URL it gives you.
2. Register in Settings: Paste this URL into Agent Invoice Settings → Developer API → Webhook Endpoint URL and save.
3. Build the Flow: Use your automation tool to parse the incoming payload's data.total and data.client_name fields and route that data to QuickBooks, Xero, Slack, Google Sheets, or wherever else you need it.

6. Integration Troubleshooting

• API returns 401 (Unauthorized): Verify your request header includes Bearer preceding your API key, and check that the key matches your active Settings key exactly.
• API returns 403 (Forbidden): Developer API access requires an active Agency Pro subscription. If your plan has downgraded or your subscription has lapsed, upgrade or renew to reactivate access.
• Webhooks not delivering: Verify your receiving endpoint accepts POST requests and returns a success response promptly. Deliveries are fire-and-forget with no automatic retries, so a failed or slow endpoint will silently miss events.