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Accounting and finance ⇄ Business productivity

Bill to Customer.io integration — real-time, two-way sync

Keep Bill and Customer.io in sync without custom scripts. Cut weeks of integration work, eliminate silent data drift, and give your team a single, reliable source of truth.

  • SOC 2 and 6 other compliance frameworks
  • POC with real engineers in minutes

Adopted by fast-scaling companies moving mission-critical data in real time

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Why teams connect Bill and Customer.io

Connect the financial records in Bill with the work happening in Customer.io, so both stay current without exports or copy-paste.

Bill holds the financial truth: who the customers are, what they were billed, what they paid. Customer.io is where part of the day-to-day work happens, and that work often involves the same customers and transactions. Without a live connection, the two drift apart, and people end up answering questions from stale copies.

Stacksync keeps Payments, Chart of Accounts, Bank Accounts, Vendor Credits and Credit Memos in Bill and Objects, Events, Segments, Campaigns in Customer.io in sync, bi-directionally and in real time. Whatever records Customer.io keeps and whatever events it produces, the overlap with Bill is mapped field by field, and a change on either side shows up on the other within seconds.

There is no middleware to build, no API rate limits to babysit, and no nightly job that leaves the morning running on yesterday's data.

Common use cases

  • 01 Write Vendors created during ERP onboarding into BILL so new payees are ready to pay without manual re-entry.
  • 02 Read Payments and payment status into a reconciliation database once bills are marked paid in BILL.
  • 03 Keep unsubscribe and subscription-preference state consistent between Customer.io and the CRM to avoid compliance gaps.
  • 04 Sync account-level objects and their person relationships for B2B messaging keyed to company attributes.

Common sync patterns

Where Customer.io collects payments or triggers charges: events land in Bill

Payment and charge activity flows into Bill as it happens, so the books reflect reality without manual reconciliation.

Where Customer.io tracks people or companies: one identity

A customer's details updated in either system update the other, so finance and the rest of the business stop maintaining two versions of the same customer.

Where Customer.io handles customer conversations: billing context in view

Front-line teams see invoice and payment status from Bill next to the customer they are helping, without logging into the finance system.

What you can sync between Bill and Customer.io

Representative objects on each side — any object or custom field can map to any target. Schemas are auto-detected; types are converted between the two systems.

Bill objects Customer.io objects How this pairing syncs
Invoices Accounts-receivable invoices sent to customers; created and read via /v3/invoices to keep billing status aligned with the ERP or CRM. Broadcasts One-off sends to segments or audiences, triggerable via API. Invoices is specific to Bill and Broadcasts to Customer.io — each maps to any object or custom field on the other side.
Customers AR customer master records; mapped to customer/account records in a CRM or ERP so finance and sales share one view. Deliveries / Messages Per-recipient message records whose lifecycle events flow out through reporting webhooks. Customers is specific to Bill and Deliveries / Messages to Customer.io — each maps to any object or custom field on the other side.
Payments Outgoing vendor payments and received customer payments; read for reconciliation and created to schedule bill pay. Newsletters Recurring email sends with performance metrics available for reporting syncs. Payments is specific to Bill and Newsletters to Customer.io — each maps to any object or custom field on the other side.
Chart of Accounts GL accounts used to code bills and invoices; typically mastered in the accounting system and written into BILL for consistent coding. People Profiles with attributes, matched on identifiers like id or email; the main write target of data syncs. Chart of Accounts is specific to Bill and People to Customer.io — each maps to any object or custom field on the other side.
Bank Accounts Funding and deposit accounts; read to reconcile payments and posted transactions against the ledger. Objects Non-person entities such as accounts or companies, related to people for account-level messaging. Bank Accounts is specific to Bill and Objects to Customer.io — each maps to any object or custom field on the other side.
Vendor Credits and Credit Memos AP and AR adjustments applied against bills and invoices; synced so balances stay accurate on both sides. Events Behavioral events sent via the Track API that trigger campaigns. Vendor Credits and Credit Memos is specific to Bill and Events to Customer.io — each maps to any object or custom field on the other side.

How changes propagate between Bill and Customer.io

Each direction of the sync is driven by what the source system can signal and what the destination accepts — detection, delivery, and expected latency below.

Bill Customer.io Sub-second propagation

DetectionBill notifies Stacksync of record changes through webhook events. Webhook event subscriptions (POST /v3/subscriptions) for bills, vendors, payments, invoices, and bank accounts, with polling on.

DeliveryEach detected change is written to Customer.io through its API, with automatic retries and rate-limit backoff.

Customer.io Bill Sub-second propagation

DetectionCustomer.io notifies Stacksync of record changes through webhook events. Reporting webhooks push message and delivery events.

DeliveryEach detected change is written to Bill through its API, with automatic retries and rate-limit backoff.

Rate-limit considerations

  • Bill: 20,000 requests per developer key per hour; login (POST /v3/login) capped at 200/hour; maximum 3 concurrent requests per developer key per organization. Spend & Expense API is a separate token at 60 calls/token/minute.
  • Customer.io: Subject to per-API rate limits documented by Customer.io.
What ships with Bill ⇄ Customer.io

Connect Bill and Customer.io for flexible, real-time data sync.

Real-time sync, workflow automation, event queues, EDI, and monitoring, for every Bill–Customer.io connection.

Real-time

Two-way sync

Changes in Bill or Customer.io instantly reflect in both systems. No stale data, no manual imports.

No-code + pro-code

Workflow automation

Trigger automated workflows whenever Bill or Customer.io data changes, update records, fire webhooks, or kick off sequences without brittle API scripts.

At scale

Event queues

Handle millions of events per minute without losing a single Bill or Customer.io record.

Observability

Monitoring

Track your Bill ⇄ Customer.io sync health, view errors, and replay failed events in one click.

Trading partners

EDI

Transform legacy EDI complexity into simple database interactions between Bill and Customer.io.

How the Bill and Customer.io connectors work

Bill

Integration surface
REST/JSON (BILL v3 Connect API)
Authentication
Session-based: POST /v3/login with username, password, organizationId, and a developer key (devKey) returns a sessionId that is passed with the devKey as headers on every subsequent call; OAuth is available for partner/embedded apps
Change detection
Webhook event subscriptions (POST /v3/subscriptions) for bills, vendors, payments, invoices, and bank accounts, with polling on createdTime/updatedTime list filters as the fallback
Capabilities
read · write · webhooks
Rate limits
20,000 requests per developer key per hour; login (POST /v3/login) capped at 200/hour; maximum 3 concurrent requests per developer key per organization. Spend & Expense API is a separate token at 60 calls/token/minute.

Customer.io

Integration surface
REST APIs split by purpose: Track API for data ingestion, App API for campaigns, people lookups, and messages
Authentication
Basic auth with site ID and API key for the Track API; bearer token for the App API
Change detection
Reporting webhooks push message and delivery events; person attribute changes are not streamed and require source-side detection
Capabilities
read · write · webhooks
Rate limits
Subject to per-API rate limits documented by Customer.io
How it works

How to connect Bill to Customer.io — three steps, no code

Configure and sync within minutes, no code. Whether you sync 50k or 100M+ records, Stacksync handles the queues, infra, and plumbing. Integrations are non-invasive and need zero setup on your systems.

  1. 01

    Connect your apps

    Authenticate Bill and Customer.io with each platform's native method — OAuth, API keys, or service accounts — plus secure options like SSH tunneling, IP whitelisting, and VPC peering.

    • OAuth 2.0
    • SSH tunnel
    • VPC peering
    Bill connected
    Customer.io connected
    OAuth 2.0
    SSH tunnel
    SSL certificate
    VPC peering
  2. 02

    Choose tables

    Pick the Bill and Customer.io objects to sync — Stacksync auto-detects both schemas, including custom fields where the platform exposes them. Sync to existing tables, or let Stacksync create new ones with ideal data types.

    • Standard objects
    • Custom objects
    • Auto-schema
    objects · Bill ⇄ Customer.io
    Customers 12,480
    Sales Orders 8,213
    Invoices 5,902
    Items 1,344
  3. 03

    Map fields

    Fields map automatically even when names and types differ. Stacksync handles transformation and type casting for you, zero configuration required.

    • Auto-map
    • Type casting
    • Transforms
    Bill Customer.io
    Company company_name text
    Email email text
    Amount amount numeric
    Created created_at timestamp
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FAQ

Bill and Customer.io integration FAQ

SECURITY

Security teams trust Stacksync

As a data company, we understand the importance of keeping your data secure. Stacksync is built with security best practices to keep your data safe at every layer, and is DPF-certified for US, EU, UK and CH data transfers.

Learn more about security
SOC 2 Type II
ISO 27001
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GDPR
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CSA STAR
DPF US-EU-UK-CH
→ SECURITY WITH BENEFITS

SSO & SCIM

Let your users access Stacksync from your centralized user management systems. Works with Okta, Azure, Google SSO and more.

Alerts

Immediately get alerted about record syncing issues over email, Slack, PagerDuty and WhatsApp. Resolve issues from a centralized dashboard with retry and revert options.

Secure connection options

Securely connects to your systems with:

OAuth 2 SSH Tunnelling SSL certificates IP Whitelisting VPN gateway VPC peering and more

Related integrations

Every pair below is a real-time, two-way sync. Search all 411 integrations available for Bill and Customer.io.

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