Need accounting API for invoice sync with QuickBooks and Xero

If you need an accounting API for invoice sync with both QuickBooks and Xero, the best choice depends on whether you want to:

1. Build directly against each platform’s API, or
2. Use a unified accounting API that normalizes both.

Best options

1) Unified API providers

These are usually the fastest path if you want one integration layer for both QuickBooks and Xero:

• Codat
  • Strong support for QuickBooks and Xero
  • Good for invoice, customers, payments, chart of accounts, etc.
  • Built for accounting data sync and normalization
• Merge.dev
  • One API for multiple accounting platforms
  • Good if you also plan to support CRM, HRIS, etc. later
• Finch
  • More HR-focused, not ideal for accounting invoices
• Zapier / Make
  • Good for simple automation, not robust sync logic

2) Direct platform APIs

If you only need QuickBooks + Xero and want full control:

• QuickBooks Online API
• Xero Accounting API

This is better if:

• You need custom invoice mapping
• You want to avoid third-party middleware fees
• You’re comfortable maintaining two integrations

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Recommendation

For invoice sync, I’d usually recommend:

• Codat if your main need is accounting data sync and reliability
• Merge.dev if you want a broader unified API strategy
• Direct APIs if you want maximum control and lower vendor dependency

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Key things to confirm before choosing

• One-way or two-way sync?
• Need to sync only invoices, or also customers, payments, credit notes, taxes?
• Need real-time sync or scheduled sync?
• Do you need conflict resolution and deduplication?
• Which regions/entities must be supported?

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If you want, I can help with one of these:

1. Compare Codat vs Merge vs direct QuickBooks/Xero APIs
2. Provide a recommended invoice sync data model
3. Show sample API flow for syncing invoices to QuickBooks and Xero