Integrations / Payments, invoicing and accounting

Use AssistCall with Invoice Ninja

AssistCall answers your business calls 24/7 and can send each call, message and booking to Invoice Ninja through Webhook, Live API actions, Zapier, Make, n8n.

Invoice Ninja: Invoice Ninja is open-source software for invoicing, quotes, payments and time tracking, used by freelancers and small businesses either hosted or self-hosted.

Connects

Example call

A client calls asking how much is left on invoice 0042. The receptionist looks it up in Invoice Ninja and tells him $350 is due on the 15th. The owner gets the call summary by email.

• During a call, the receptionist searches your Invoice Ninja clients by the caller's phone number to see who is calling.
• When a caller reads out an invoice number, the receptionist looks it up in Invoice Ninja and tells them the balance and due date.
• When AssistCall captures a lead, a Zap or n8n workflow uses Invoice Ninja's Find or Create Client, so the caller is ready for a quote.

How it connects

• Webhook: Signed JSON for every call, message and booking, sent to any HTTPS URL you choose.
• Live API actions: During the call, the receptionist calls the app's API with your key to look up or create records.
• Zapier: Send AssistCall events to a Zap (Webhooks by Zapier, Catch Hook), then use the app's Zapier actions. Needs a paid Zapier plan.
• Make: Start a Make scenario with a custom webhook and use the app's Make modules.
• 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 Invoice Ninja's API

• Self-serve API: you can create a key in your account
• Style: REST (JSON), v5 API
• Authentication: API token sent in the X-API-TOKEN header. Tokens stay valid until you delete them.
• On Zapier: yes. On Make: yes.

Create a token under Settings > Account Management > API Tokens. On the hosted service, REST API access needs a paid plan (Pro or above); self-hosted installs include it. Useful live lookups: GET /api/v1/clients?filter={caller_phone} searches client names and contact names, emails and phone numbers, as a partial match on the stored text, so numbers need to be stored in a format that matches caller ID. GET /api/v1/invoices?number={invoice_number} returns that invoice with its balance and due date, and ?payable={client_id} lists a client's unpaid invoices. Invoice Ninja's API docs also show an X-Requested-With: XMLHttpRequest header, but AssistCall sends only the token header, so test a lookup before going live. Webhooks are set up in Settings > Account Management. Zapier, Make and n8n all have Invoice Ninja apps.

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

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

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.
• 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.

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.