How to Automate Invoicing Across QuickBooks, Xero, and 30+ Accounting Platforms with a Unified API
October 21, 2025
Modern SaaS products often need to generate invoices, reconcile payments, and sync financial data across multiple accounting systems. But every provider — from QuickBooks and Xero to NetSuite and Zoho — uses different objects, tax models, and APIs, creating unnecessary friction for developers and finance teams.
A unified API eliminates that complexity. Unified.to connects to your customers' accounting applications and provides normalized, real-time accounting objects — invoices, payments, tax rates, and contacts — so your product can automatically create, send, and reconcile invoices without per-vendor code.
When to Use Automated Invoicing
With a unified API, you can:
- Automatically generate and send invoices for product usage or subscriptions
- Sync customers, items, tax rates, and payments across ERPs and accounting tools
- Standardize reporting and analytics across multiple accounting providers
Normalized Accounting Objects
Unified.to provides consistent schemas across all supported accounting platforms:
| Object | Description | Key Fields |
|---|---|---|
| invoice | Customer invoice with line items, totals, and status | id, invoice_number, customer_id, currency, status (DRAFT, SENT, PAID, VOID), issue_date, due_date, line_items[] (item_id, description, quantity, unit_price, tax_rate_id), subtotal, tax_total, total, balance, pdf_url |
| contact | Billing entity for invoices | id, name, emails, company_name, billing_address, shipping_address, tax_number |
| item | Product or service used on invoices | id, name, sku, unit_price, tax_rate_id, income_account |
| payment | Payment applied to an invoice | id, invoice_id, amount, currency, payment_date, method, transaction_id, status |
| credit_note | Negative invoice for refunds or adjustments | id, customer_id, line_items[], total, applied_to_invoice_id |
| tax_rate | Tax configuration object | id, name, rate, jurisdiction, inclusive |
| webhook | Real-time change delivery | object_type, event, sig, nonce, type |
Data Flow for Automated Invoicing
Unified.to standardizes how financial events and invoices flow through your product:
- Connect the customer's accounting system via Unified Connect to receive a
connection_id. - Sync master data such as customers, items, and tax rates through normalized endpoints.
- Create invoices from business triggers — usage metering, subscription renewal, or order creation.
- Send invoices through the customer's chosen provider (email, PDF, or portal).
- Capture payments in real time via webhooks and automatically apply them to open invoices.
Supported Accounting & Payment Platforms
Unified.to supports 32+ accounting and finance integrations, including:
QuickBooks, Xero, FreshBooks, Sage Intacct, NetSuite, Wave, MYOB, Pennylane, Holded, Zoho Books, Zoho Invoice, Microsoft Dynamics 365 (Business Central, Sales, and Customer Engagement), Shopify, WooCommerce, BigCommerce, SquareUp, Stripe, GoCardless, PayPal, Chargebee, Brex, Ramp, and more.
See the full list of supported Accounting integrations and explore the Accounting API documentation for implementation details.
Why Product Teams Choose Unified.to
For PMs and engineers building SaaS or fintech products:
- One build, 30+ systems — launch invoicing across every accounting platform
- Unified schema — invoices, contacts, and payments all follow consistent data models
- Real-time sync — webhook and DB sync keep balances and statuses up to date
- Automation-ready — trigger billing events from usage, subscriptions, or external systems
Launch automated invoicing and accounting workflows in days — not months.
Start your free 30-day trial or book a demo to see how Unified.to accelerates financial automation.