Automate Overdue Invoice Alerts from Pennylane to Slack

Stop losing money on forgotten overdue invoices. This n8n workflow automatically monitors your Pennylane account daily and sends instant Slack alerts when customer invoices are 7+ days past due, complete with payment details and direct PDF links.

What this workflow does

Running automatically at 9 AM daily, this workflow connects to your Pennylane accounting platform to fetch all customer invoices and identify unpaid ones exceeding their deadline by 7 or more days. When overdue invoices are detected, it immediately sends a comprehensive Slack notification containing the invoice number, outstanding amount, days overdue, and a direct link to the invoice PDF. If no invoices require follow-up, the workflow ends silently without unnecessary notifications.

Use cases

• Finance teams managing multiple client accounts who need systematic overdue invoice tracking
• Freelancers using Pennylane who want automated payment follow-up reminders
• Small businesses looking to improve cash flow management through timely invoice collection
• Accounting departments requiring daily visibility into overdue receivables

Technical details

This workflow leverages n8n's scheduling capabilities with Pennylane API integration and Slack notifications. Built using HTTP Request nodes for Pennylane API calls, Code nodes for invoice filtering logic, Set nodes for data processing, conditional If nodes for workflow control, and Slack integration for alerts.

Requirements: Pennylane account with Essentiel plan or higher, API token with customer_invoices:all scope, and optional Slack workspace access.

Setup: Simply import the workflow, configure Header Auth credentials with your Pennylane Bearer token, select your preferred Slack channel, and optionally adjust the 9 AM schedule trigger.

Customization: Easily modify the 7-day threshold in the Code Filter node, change scheduling times, or replace Slack notifications with email, Telegram, or other communication channels. Part of a comprehensive 3-workflow Pennylane billing automation suite for complete invoice management.