Automated invoice payment reminders with Google Sheets and Gmail

How It Works ⚙️

This workflow systematically ensures you never miss sending an invoice reminder:

1. Daily Schedule Trigger: ⏰ The workflow starts automatically at a set time each day (e.g., every morning). This ensures continuous monitoring of your invoice statuses.
2. Read Invoice Data (Google Sheets): 📊 The workflow connects to your specified Google Sheet to retrieve a list of all your invoices and their details. Ensure your sheet has required columns like InvoiceID, ClientName, ClientEmail, Amount, DueDate, and Status.
3. Filter & Prepare Reminders (Function): 🧹 This is the core logic. It processes each invoice row:
   • Compares the DueDate with the current date.
   • Identifies invoices that are due soon (e.g., within 3 days) or are already overdue (e.g., up to 7 days past due).
   • Skips invoices marked as 'Paid'.
   • Prepares a custom subject line and email body for each relevant reminder.
4. If Invoices to Remind?: 🚦 This node acts as a gate. If the previous step found any invoices needing reminders, the workflow proceeds. If not, it stops gracefully.
5. Send Invoice Reminder (Gmail): 📧 For each filtered invoice, this node sends a personalized email reminder to the client. The email uses the dynamic subject and body prepared in the 'Filter & Prepare Reminders' step.

How to Set Up 🛠️

Follow these steps carefully to get your "Automated Invoice Reminder" workflow up and running:

1. Import Workflow JSON:

   • Open your n8n instance.
   • Click on 'Workflows' in the left sidebar.
   • Click the '+' button or 'New' to create a new workflow.
   • Click the '...' (More Options) icon in the top right.
   • Select 'Import from JSON' and paste the entire JSON code provided in the previous response for this workflow.

2. Configure Daily Schedule Trigger:

   • Locate the 'Daily Schedule Trigger' node (1. Daily Schedule Trigger).
   • Adjust 'interval', 'value', and 'timezone' to your preferred daily reminder time (e.g., every 24 hours at 9 AM in your local timezone).

3. Configure Read Invoice Data (Google Sheets):

   • Locate the 'Read Invoice Data (Google Sheets)' node (2. Read Invoice Data).
   • Credentials: Select your existing Google Sheets OAuth2 credential or click 'Create New' to set one up. Replace YOUR_GOOGLE_SHEETS_CREDENTIAL_ID with the actual ID or name of your credential from your n8n credentials.
   • Sheet ID: Replace YOUR_GOOGLE_SHEET_ID with the actual ID of your Google Sheet where invoice data is stored.
   • Range: Ensure the 'range' (e.g., Invoices!A:F) correctly covers all your invoice data. Crucially, ensure your Google Sheet has columns with exact names: InvoiceID, ClientName, ClientEmail, Amount, DueDate (in a parsable date format like YYYY-MM-DD), and Status (e.g., 'Pending', 'Paid').

4. Configure Filter & Prepare Reminders (Function):

   • Locate the 'Filter & Prepare Reminders' node (3. Filter & Prepare Reminders).
   • Date & Field Names: Review the functionCode inside the node. Adjust the variable names (e.g., invoice.InvoiceID, invoice.DueDate) if your Google Sheet uses different column headers than the defaults assumed in the code.
   • Reminder Window: You can modify remindBeforeDays (e.g., 3 days before) and remindAfterDays (e.g., 7 days after) to adjust how many days before/after the due date reminders are sent.
   • Email Content: Modify the subjectPrefix and bodyText within the code to customize the reminder message for 'due soon' and 'overdue' invoices.

5. Configure Send Invoice Reminder (Gmail):

   • Locate the 'Send Invoice Reminder (Gmail)' node (5. Send Invoice Reminder).
   • Credentials: Select your existing Gmail OAuth2 credential or click 'Create New'. Replace YOUR_GMAIL_CREDENTIAL_ID with the actual ID or name of your credential from your n8n credentials.
   • From Email: Replace [email protected] with the email address you want the reminders to be sent from.
   • Email Content: The 'subject' and 'html' fields are dynamically generated by the previous 'Function' node (={{ $json.subject }} and ={{ $json.body }}). You can further customize the HTML email template here if needed.

6. Review and Activate:

   • Thoroughly review all node configurations. Ensure all placeholder values (like YOUR_...) are replaced and settings are correct.
   • Click the 'Save' button in the top right corner.
   • Finally, toggle the 'Inactive' switch to 'Active' to enable your workflow. 🟢 Your automated invoice reminder is now live and ready to improve your cash flow!

Troubleshooting Tips: 💡

• Execution History: Always check the 'Executions' tab in n8n for detailed error messages if the workflow fails.
• Google Sheet Data: Ensure your Google Sheet data is clean and matches the expected column headers and date formats.
• Function Node Logic: If invoices aren't being filtered correctly, the Function node is the place to debug. Use the 'Test Workflow' feature to inspect the data flowing into and out of this node.
• Credential Issues: Double-check that all credentials are correctly set up and active in n8n.