SAP S/4HANA and AvidXchange integration

What moves between them

The main flow runs from SAP S/4HANA into AvidXchange. Vendor master records, GL accounts, and cost centers are pushed from SAP into AvidXchange so AP staff can code invoices against valid accounts, and these reference records sync first because a missing vendor in AvidXchange means a payment cannot be routed. Supplier invoices then move from SAP into AvidXchange for approval and payment, carrying their PO reference for matching where one exists. After AvidXchange executes payment, ml-connector pulls the settled payment record (check number, ACH trace, or virtual card detail) back and posts it against the matching supplier invoice in SAP. GL codes are read-only in AvidXchange, so the chart of accounts is mastered in SAP and never written back from AvidXchange.

How ml-connector handles it

ml-connector stores both credential sets encrypted and bridges SAP OAuth 2.0 client credentials, refreshed before the roughly 12-hour token expires, with the AvidXchange Company and User tokens. Because every SAP write needs an X-CSRF-Token, it fetches the token and session cookies on a GET, presents them on each supplier invoice create or payment posting, and re-fetches and retries if SAP returns 403. Both systems are pull-only, so it polls SAP supplier invoices and vendor changes with a $filter on LastChangeDateTime and polls the AvidXchange payment sync endpoint every fifteen to thirty minutes rather than waiting for a push. Vendors and cost centers map first so every invoice references a payee and account that already exist on the AvidXchange side. SAP returns HTTP 429 with a Retry-After header when throttled, so ml-connector backs off with jitter and retries, and SAP's own duplicate detection rejects a re-sent invoice with the same reference, company code, and fiscal year. Every record carries a full audit trail and can be replayed if a downstream call fails.

A real-world example

A mid-market property management firm with about 400 staff runs SAP S/4HANA Cloud for finance across a portfolio of buildings and uses AvidXchange to capture, approve, and pay supplier invoices. Before the integration, AP clerks keyed each approved bill from AvidXchange back into SAP by hand and re-typed check and ACH numbers after payments cleared, which left the supplier ledger lagging and made bank reconciliation slow at month-end. With SAP S/4HANA and AvidXchange connected, vendors, GL accounts, and cost centers flow into AvidXchange for accurate coding, invoices move over for approval, and settled payments post back into SAP automatically. The supplier ledger stays current, reconciliation is faster, and the duplicate manual entry is gone.

What you can do

• •Push SAP S/4HANA vendor master records into AvidXchange so every payee exists before invoices are coded and paid.
• •Sync GL accounts and cost centers from SAP into AvidXchange so AP staff code invoices against valid accounts and dimensions.
• •Move supplier invoices from SAP into AvidXchange for approval routing and payment, with PO references carried for matching.
• •Read settled check, ACH, and virtual card payment records back from AvidXchange and post them against the matching invoices in SAP.
• •Bridge SAP OAuth 2.0 and the X-CSRF-Token write handshake to AvidXchange token auth, polling both systems on the schedule you set.

Questions

Which direction does data move between SAP S/4HANA and AvidXchange?

Most data moves from SAP S/4HANA into AvidXchange. Vendors, GL accounts, cost centers, and supplier invoices are pushed into AvidXchange, while settled payment records flow back the other way into SAP. GL codes are read-only in AvidXchange, so the chart of accounts is always mastered in SAP and never overwritten from the AP side.

How does the integration handle writing supplier invoices into SAP?

SAP requires an X-CSRF-Token on every write, which ml-connector fetches on a prior GET along with the session cookies. It presents that token on each supplier invoice create and payment posting, and if SAP returns a 403 it re-fetches the token and retries. SAP's built-in duplicate detection also rejects a re-sent invoice with the same reference, company code, and fiscal year, which guards against double posting.

Do either of these systems support webhooks, or is this polling?

Neither side offers a confirmed public webhook for this connector, so the sync is poll-based. ml-connector reads SAP changes using a $filter on LastChangeDateTime and polls the AvidXchange payment sync endpoint on a set interval. If the customer licenses SAP BTP with Event Mesh, near-real-time SAP events can be added, but the default model is scheduled polling on both sides.