Custom Fields API: Enhancing QuickBooks Online with Flexible Metadata

The Custom Fields API in QuickBooks Online allows developers to extend data models with flexible metadata. This can be applied across entities like customers, invoices, and vendors. The API combines GraphQL and REST layers to define custom fields and attach them to transactions and entities. Custom fields can unlock various business scenarios, such as tagging sales with project codes or tracking customer loyalty tiers. Required OAuth scopes include app-foundations.custom-field-definitions.read, app-foundations.custom-field-definitions, and com.intuit.quickbooks.accounting.