> ## Documentation Index > Fetch the complete documentation index at: https://docs.paypathiq.com/llms.txt > Use this file to discover all available pages before exploring further. # Change notification > PayPathIQ sends this request to your configured endpoint when a Customer or Receivable change commits. It carries only the event identity, type, resource reference and revision: read the resource with your API key for detail. Verify the PayPathIQ-Signature header, which is t=,v1=.' keyed with your signing secret>; during the 24 hours after a rotation it carries a v1 value for each of the current and previous secrets. Reject timestamps more than 5 minutes old. Respond with any 2xx status within 5 seconds. Redirects are not followed. Any other outcome is retried with backoff up to 8 attempts over about two days, then abandoned: recover through the change feed. Delivery is at least once and unordered: discard repeated eventId values and compare revision before applying. Grants, scopes and the destination are re-checked on every attempt; a revoked grant or unsafe destination disables the endpoint. ## OpenAPI ````yaml /generated/inbound-api-v1.openapi.json webhook changeNotification openapi: 3.1.0 info: description: >- Send Customers, Receivables, and Payment observations and related financial evidence from your source system to PayPathIQ, one record at a time or as bounded asynchronous batches, and read back changes. Every operation listed here is implemented; capabilities that are not implemented are not listed. Start in sandbox with a sandbox key and synthetic data. Every error type links to a page at https://docs.paypathiq.com/problems/{code}. title: PayPathIQ Inbound Receivables API version: 1.0.0 servers: - description: Sandbox url: https://api.sandbox.paypathiq.com - description: Production url: https://api.paypathiq.com security: - BearerAuth: [] tags: - description: >- PayPathIQ-owned delivery of receipts to the accounting Source, with acknowledgement kept separate. name: Receipt delivery - description: People and businesses that owe one Client. name: Customers - description: Independently recoverable Receivables. name: Receivables - description: Immutable evidence of external payments, refunds, and reversals. name: Payment observations - description: >- Ordered Source balance snapshots for transaction and snapshot-only connections. name: Balance snapshots - description: >- Bounded asynchronous ingestion of up to 100 records with exact per-record outcomes. name: Batches - description: >- Verified complete-book declarations that flag and hold Receivables missing from the book. name: Complete books - description: Durable, resumable record of committed Customer and Receivable changes. name: Changes - description: >- Optional signed, minimal notifications that a Customer or Receivable changed. name: Webhooks - description: >- Fixed-amount hosted payment pages through the Client's own payment provider merchant. name: Payment requests - description: >- Partner-owned delivery of confirmed Payments to accounting, kept separate from accounting acceptance. name: Payment delivery - description: Explicit Receivable pause and closure commands. name: Receivable lifecycle - description: >- Explicit, revisioned instructions that let PayPathIQ begin recovery for a Receivable. name: Recovery instructions - description: >- Permissioned working collection position, holds, commitments and action outcomes, separate from the Source representation. name: Collection summaries - description: Whether accepted source evidence is recent enough to act on. name: Source freshness - description: This machine-readable API contract. name: Specification paths: {} components: securitySchemes: BearerAuth: bearerFormat: ppiq_test__ or ppiq_live__ description: >- Integration-owned environment-specific API key. Never paste a production key into documentation tools. scheme: bearer type: http ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.