Chaining IDs across API calls

Paystand uses several ID types. Store the right ID from each response to avoid broken links in your ERP.

ID reference

ID	Where you get it	Use for
Merchant customer_id	Dashboard → Integrations	X-CUSTOMER-ID header on every call
payerCustomer.id	Create/List/Get Customer	payerCustomerId on receivables; credit memo customer scope. Not the same as payment.payerId unless that payer is listed under your merchant — wrong IDs return 401 on Get Customer.
extCustomerId	Your ERP customer key (sent on create)	Alternative to payerCustomerId on receivable create/update
receivable.id	Create/Get/List Receivable	Attachments, cancel, receivable transactions
extId / invoice key	Your ERP invoice number	Receivable create; filter helpers on receivable list
payment.id	Payment webhooks or List Payments	Merchant fee lookup (fees[]), payer fee split (feeSplit), refunds, reconciliation
fee.id	Fee webhooks or List Fees	GL lines for merchant processing fees (not payer recoup)
feeSettingPlan.id	Get Fee Setting Plan when you have an ID; or infer rates via Split Fees	Pre-payment payer fee estimates
creditMemo.id	Credit memo APIs	Cancel/activate credit memos. Create requires extKey, status, numeric amount / amountRemaining, and MM-DD-YYYY dates — see Create Credit Memo and the Credit memo lifecycle guide
transfer.id	List/Get Transfer	Payout reconciliation

Example flow

1. POST /payerCustomers → save id as payerCustomerId.
2. POST /receivables/create with payerCustomerId (or extCustomerId) → save receivable.id.
3. Payment webhook includes payment.id → GET /payments/{id} for details.
4. Merchant processing fee webhook references payment → GET /fees with filter on resourceId when authorized, GET /payments/{id} embedded fees[], or use fee id from the event payload. For payer-side split, read feeSplit on the same Get Payment response.
5. Pre-payment payer fee split → POST /feeSplits/splitFees with payment subtotal and optional payerId / invoiceId / feeSettingPlanId — see Split Fees. For single-rail estimates only, POST /feeSplits/computeFees accepts feeType + subtotal + currency (no payer/invoice context).

ERP keys vs Paystand IDs

Prefer storing both your ERP key (extCustomerId, invoice extId) and Paystand’s id. If you re-sync from ERP, match on ERP keys; use Paystand id for all subsequent API paths (/receivables/{id}/cancel, etc.).

Related

• ERP integration overview
• Payment and fee reconciliation