Integrations / Payments, invoicing and accounting

Use AssistCall with BILL

AssistCall answers your business calls 24/7 and can send each call, message and booking to BILL through Webhook, n8n.

BILL: BILL is accounts payable, accounts receivable and spend management software that small and midsize businesses use to pay bills, send invoices and get paid.

Connects

Example call

A supplier calls asking when his invoice will be paid. AssistCall takes a message with his company, invoice number and urgency. An n8n workflow sends it to the AP inbox, and the controller gets the summary and recording link by email.

• When AssistCall captures a new lead, an n8n workflow signs in to BILL's API and creates the caller as a customer in BILL accounts receivable.
• When a vendor or customer leaves a billing message, AssistCall's message.taken event starts an n8n workflow that sends it to your AP or AR inbox with the caller, reason and urgency.
• Forward your accounts line to AssistCall at busy times, so calls about payments become messages with the caller's number and reason instead of voicemails.

How it connects

• Webhook: Signed JSON for every call, message and booking, sent to any HTTPS URL you choose.
• n8n: Start an n8n workflow with a webhook node, then call the app with its node or an HTTP request.
• Call forwarding: Forward your business line to AssistCall when busy, after hours or always. Works with any carrier.

About BILL's API

• Self-serve API: you can create a key in your account
• Style: REST (JSON), BILL v3 API
• Authentication: A developer key plus a session from POST /v3/login. Sessions expire after 35 minutes of inactivity, or 48 hours for sync-token sign-in.
• On Zapier: no. On Make: no.

An administrator can generate a production developer key in the BILL web app (Settings > Sync & Integrations > Manage Developer Keys). Every API session starts with a sign-in call that returns a sessionId, and that session expires after 35 minutes idle. AssistCall's live API lookup sends one fixed header and has no sign-in step, so it can't call BILL. We found no BILL app on Zapier or Make. An n8n workflow can sign in and then call the API with the HTTP Request node. BILL webhooks cover vendors, bills, payments and AR invoices.

Not included: no one-click BILL app, no listing in BILL's marketplace, no two-way sync, and no partnership with BILL Holdings, Inc..

Researched by the AssistCall team and checked against BILL Holdings, Inc.'s public pages on October 24, 2026. BILL is a trademark of BILL Holdings, Inc.. AssistCall is an independent product of Starling Global LLC and is not affiliated with, endorsed by, sponsored by or approved by BILL Holdings, Inc..

More Payments, invoicing and accounting integrations

• PayPal: PayPal is an online payments service that small businesses use to accept payments and send invoices that customers can pay online.
• QuickBooks Online: QuickBooks Online is Intuit's cloud accounting software that small businesses use for invoicing, payments, expenses and bookkeeping.
• Square: Square is Block's payments and point-of-sale platform that small businesses use to take card payments, send invoices and keep a customer directory.
• Stripe: Stripe is an online payments platform that businesses use to take card payments, bill customers, run subscriptions and send invoices.
• Authorize.net: Authorize.net is Visa's payment gateway that small businesses use, through a merchant account, to accept card and eCheck payments online, in person and over the phone.
• FreshBooks: FreshBooks is cloud invoicing and accounting software for freelancers and service-based small businesses, with time tracking, estimates and online payments.

All product and company names in this directory are trademarks or registered trademarks of their respective owners, used only to identify systems AssistCall can send call information to or receive information from. Their use does not imply any affiliation with or endorsement by their owners. AssistCall connects using signed webhooks, the business's own API keys, automation platforms (Zapier, Make, n8n) the business sets up in its own account, and call forwarding. AssistCall does not provide one-click connectors, marketplace apps, certifications or two-way record or calendar sync, and does not sign HIPAA business associate agreements. Vendor features, plans and API access can change; information last checked October 24, 2026.