Workday Financial Management and BILL integration

What moves between them

The main flow runs from BILL into Workday Financial Management. Unpaid bills created or updated in BILL are polled on your schedule and posted into Workday as supplier invoice records, mapped to the matching Workday vendors and GL accounts. Vendor reference data is aligned in both directions so bill line items land on valid Workday expense accounts and worktags. Payments made in BILL can also trigger payment records in Workday if needed. Bill data flows read-only from BILL into Workday, so ml-connector does not write bills back into BILL from Workday.

How ml-connector handles it

ml-connector stores both credential sets encrypted and refreshes the Workday OAuth2 token on a schedule, using SOAP to create supplier invoices in Workday from BILL bill records because Workday REST cannot handle the full invoice structure that AP requires. On the BILL side it uses REST to read bills and vendors, and it maps BILL vendor IDs to Workday supplier records, so each bill line item references a GL account and cost center that already exist in Workday. Because BILL supports webhooks, ml-connector can subscribe to bill.created and bill.updated events to catch changes in near-real time, though it also polls on a fallback schedule to ensure no event is missed. BILL rate limits via HTTP 429, so ml-connector backs off exponentially and retries, and it tracks Workday ISU account security group membership so credential loss is caught before it causes an outage. Every bill carry a full audit trail and can be replayed if a downstream Workday call fails.

A real-world example

A professional services firm uses Workday Financial Management for vendor management and general ledger, and uses BILL to automate AP workflows for expense invoices from hundreds of suppliers across multiple offices. Before the integration, the accounts payable team received approved bills from BILL and manually entered them into Workday as supplier invoices, then re-checked vendor accounts and GL codes, a task that took two to three days per week. With BILL and Workday Financial Management connected, each bill is posted into Workday automatically within minutes of approval in BILL, mapped to the correct cost center for each office and the vendor's standard GL codes. The AP team now enters invoices only once, in BILL, and closes their books faster because Workday already has the complete bill record.

What you can do

• •Post approved bills from BILL into Workday Financial Management as supplier invoice records, mapped to the correct vendors and GL accounts.
• •Keep BILL and Workday vendor reference data aligned so bill line items land on valid expense accounts.
• •Authenticate Workday with SOAP Integration System User credentials or OAuth2, and BILL with session token login.
• •Catch new and updated bills from BILL via webhooks, with fallback polling to ensure no bill is missed.
• •Validate vendor accounts and GL codes in Workday before posting, with automatic retry and a full audit trail on every bill.

Questions

Which direction does data move between Workday and BILL?

The main flow is BILL into Workday Financial Management. Bills created or updated in BILL are posted into Workday as supplier invoices, while vendor reference data is aligned in both directions. ml-connector does not write bills back to BILL from Workday.

Does ml-connector use webhooks or polling to catch new bills?

ml-connector subscribes to BILL webhooks for bill.created and bill.updated events to catch changes in near real time. It also polls on a fallback schedule to ensure no bill is missed, since webhooks alone should not be the only source of truth in a financial integration.

How does ml-connector handle authentication differences between BILL and Workday?

BILL uses session token authentication obtained by posting login credentials, and Workday uses either SOAP WS-Security or OAuth2 bearer token. ml-connector stores both credential sets encrypted, refreshes tokens as they expire, and presents the correct credentials to each system on every call.