Automated Invoice Creator with Google Sheets and Email Payment Reminder System

This n8n workflow automates the process of creating invoices, tracking their payment status in a Google Sheet, and sending automated payment reminders via email. It's designed to streamline invoicing and follow-up, reducing manual effort and ensuring timely payments.

What it does

1. Schedules Execution: The workflow runs periodically (e.g., daily, weekly) to check for pending invoices.
2. Reads Invoice Data: It connects to a specified Google Sheet to retrieve invoice details, including customer information, invoice amount, due date, and payment status.
3. Processes Invoices:
   • It filters invoices based on their payment status (e.g., "Pending", "Overdue").
   • For new invoices, it might generate and send the initial invoice.
   • For overdue invoices, it prepares a payment reminder.
4. Sends Email Reminders: Based on the invoice status, it constructs and sends personalized email reminders to customers.
5. Updates Google Sheet: After sending reminders or processing invoices, it updates the Google Sheet with the latest payment status or reminder sent date.

Prerequisites/Requirements

• n8n Instance: A running n8n instance (self-hosted or cloud).
• Google Account: A Google account with access to Google Sheets.
  • You will need to create a Google Sheet to store your invoice data. The sheet should ideally contain columns such as Invoice ID, Customer Name, Customer Email, Amount, Due Date, Status (e.g., "Pending", "Paid", "Overdue"), and potentially Last Reminder Sent.
• SMTP Credentials: Access to an SMTP server for sending emails. This could be a traditional email service (Gmail, Outlook, SendGrid, etc.) or a custom SMTP setup.

Setup/Usage

1. Import the Workflow:
   • Download the provided JSON file.
   • In your n8n instance, go to "Workflows" and click "New".
   • Click the three dots menu (...) in the top right and select "Import from JSON".
   • Paste the workflow JSON or upload the file.
2. Configure Credentials:
   • Google Sheets: You will need to set up a Google Sheets credential.
     • Click on the "Google Sheets" node.
     • Under "Credentials", select "Create New".
     • Choose "Google Sheets API" and follow the authentication steps (OAuth2 is recommended). Ensure you grant access to your Google Sheets.
   • Send Email: You will need to set up an Email (SMTP) credential.
     • Click on the "Send Email" node.
     • Under "Credentials", select "Create New".
     • Enter your SMTP server details (host, port, user, password, security).
3. Customize Google Sheet Node:
   • In the "Google Sheets" node, select the correct "Spreadsheet ID" and "Sheet Name" where your invoice data is stored.
   • Adjust the "Operation" and "Resource" as needed (e.g., "Read" to get data, "Update" to change status).
4. Customize Code Node (if present):
   • If there's a "Code" node, it likely contains logic for filtering, formatting, or determining email content. Review and adjust the JavaScript code to match your specific business rules and data structure.
5. Customize Switch Node:
   • The "Switch" node will likely contain conditions to route the workflow based on invoice status. Configure the conditions to match the values in your Google Sheet (e.g., {{ $json.status === 'Pending' }} or {{ $json.status === 'Overdue' }}).
6. Customize Send Email Node:
   • Configure the "To" address using an expression like {{ $json.customerEmail }} to dynamically pull the recipient's email from the Google Sheet data.
   • Customize the "Subject" and "Body" of the email to create your invoice or reminder message. You can use expressions to insert dynamic data (e.g., {{ $json.customerName }}, {{ $json.amount }}, {{ $json.dueDate }}).
7. Configure Cron Trigger:
   • Adjust the "Cron" node to define how often the workflow should run (e.g., daily at a specific time, every weekday).
8. Activate the Workflow: Once all configurations are complete, activate the workflow. It will start running according to the schedule defined in the "Cron" node.

This workflow provides a robust foundation for automating your invoicing and payment reminder process, ensuring you stay on top of your receivables.