How a Company in Copenhagen Solved a Problem Where a Company Spent More Than 25 Hours per Month Generating Invoices Manually Using Make

In today’s fast-paced business environment, time is money—and few processes consume as much of it as manual invoice generation. 📄 This case study reveals how a mid-sized logistics SME in Copenhagen managed to eliminate over 25 hours of repetitive monthly work by automating their invoicing process with Make, integrated seamlessly through RestFlow’s Automation-as-a-Service. If you’re a startup CTO, operations specialist, or automation engineer, this article will guide you step-by-step in understanding and implementing a robust invoice automation workflow that integrates your existing tools and boosts efficiency.

We’ll dive deep into their initial challenges, the solution architecture, detailed workflow steps with Make, and the tangible results that transformed their finance and operations departments. Plus, you’ll find valuable comparisons and practical tips to start your own automation journey.

Ready to transform your invoicing process? Explore the Automation Template Marketplace and see how others have automated similar workflows.

The Problem: Manual Invoice Generation Wasting 25+ Hours Monthly

The client is a well-established logistics SME based in Copenhagen, Denmark, specializing in freight forwarding and supply chain management services. Their finance and operations departments were responsible for generating client invoices each month—a critical, yet time-consuming task.

Before automation, invoice generation was an entirely manual process taking more than 25 hours every month, spread across multiple staff members. The team had to:

• Manually collect shipment data from their cloud ERP.
• Cross-check pricing agreements stored in Google Sheets.
• Generate invoices by compiling data in Excel spreadsheets.
• Email invoices to clients individually via Gmail.

This manual method resulted in several pain points:

• High time expenditure: 25+ hours per month spent solely on invoicing, reducing staff availability for strategic tasks.
• Errors & discrepancies: Inaccurate pricing and manual data entry caused invoice errors about 8% of the time, leading to delays in payment.
• Delayed invoicing: Invoices were often sent late due to workload, affecting cash flow and client satisfaction.
• Lack of visibility: Management had no real-time view of invoice status, creating challenges for forecasting.

This impacted both revenue flow and operational efficiency, motivating the client to seek an automated invoicing solution integrating their existing systems.

Our Approach: Discovery and Automation Proposal

RestFlow began with a thorough discovery phase, collaborating with the client’s finance and operations teams to map out the entire invoice generation process. We identified:

• Key data sources: ERP (cloud-based), Google Sheets for contract rates, Gmail for communication.
• Repetitive manual tasks, prone to human error.
• Critical pain points causing delays and errors.

We proposed automation using Make (formerly Integromat) due to its visual workflow builder, extensive connectors, and ability to handle complex logic with conditional branching—optimizing their existing toolset without costly replacements.

The high-level architecture consisted of:

• Scheduled triggers to start invoice generation monthly.
• Data extraction & validation from ERP and Google Sheets.
• Transformation logic to calculate pricing and apply discounts.
• Automated invoice creation in PDF via a document generation service.
• Automated email dispatch via Gmail.
• Slack notifications to finance team on completion or errors.
• Error handling with retries and fallback logging.

This comprehensive, modular workflow ensured robustness, scalability, and easy maintenance under RestFlow’s Automation-as-a-Service umbrella covering design, hosting, monitoring, and ongoing support.

The Solution: Architecture & Workflow

Global Automation Architecture Overview

The core architecture leverages Make’s orchestration platform as the central workflow engine with the following components:

• Trigger: A time-based scheduler in Make initiates the workflow at the start of each billing period.
• ERP system: API calls fetch shipment and delivery data needed for invoicing.
• Google Sheets: Access pricing agreements and contract details via Google Sheets API.
• Document generation: Utilizes a PDF generation module integrated within Make to create professional invoices.
• Gmail: Automatically sends invoices as email attachments to clients.
• Slack: Sends confirmation or error alerts to the finance Slack channel.
• Logging repository: Backup logs stored in Google Sheets for audit and troubleshooting.

End-to-End Workflow Description

1. Scheduled Trigger: Make’s scheduler triggers the workflow on the 1st of every month at 7:00 AM CET.
2. Fetch Shipment Data: The ERP API is called with filters for the current billing period, returning shipment details per client.
3. Retrieve Pricing Info: Google Sheets module reads per-client pricing contracts and discount terms.
4. Data Validation & Calculation: The scenario validates data completeness, calculates prices with conditional discounts or surcharges, and formats line items.
5. Generate Invoice PDF: The invoice template is populated dynamically; PDF is generated.
6. Send Invoice Email: Gmail module emails the PDF invoice to the client’s contact email with a configurable subject and body.
7. Log & Notify: Successful delivery is logged in Google Sheets; Slack notification is sent to finance.
8. Error Handling: If any step fails, the error is logged and a Slack alert is sent for immediate review.

This workflow replaces manual entry with automated, reliable invoice generation that integrates all involved services.

Step-by-Step Node Breakdown 🚀

1. Scheduler Trigger Node

Creates the monthly trigger at a fixed date/time (ISO timestamp). No inputs. Initiates the entire process automatically.

2. ERP API Connector Node

Trigger: Scheduler output.
Function: Uses REST API GET requests with query parameters (e.g., ?startDate=first_of_month) to retrieve shipment data.
Data Output: JSON array of shipments keyed by client IDs with fields like shipment_id, date, weight, destination.
Config Details: OAuth 2.0 credentials stored securely. Uses pagination with loop.

3. Google Sheets Read Node 🧾

Role: Reads pricing and contract data from a shared spreadsheet.
Details: Filters rows using client ID matching, retrieves hourly rates, fixed fees, and discount logic.
Expression Mapping: Maps client ID from ERP node; outputs structured rate data.

4. Data Transformation & Validation Node

Executes inline JavaScript code in Make’s function module.
Tasks include validating fields (non-empty), applying discount rules (e.g., 5% discount if shipments > 50), calculating total cost.

5. Document Generation Node

Populates a PDF invoice template with variables from previous steps:
– Client name and address
– Invoice number generated via Make’s UUID function
– Line items with shipment details
– Totals and tax calculations.

6. Gmail Send Email Node 📧

Input: Client email address, PDF invoice attachment, email subject/body.
Output: Confirmation on successful send.
Configuration: Uses OAuth credentials with “Send email” scope. Template variables used for personalized emails.

7. Logging to Google Sheets Node

Appends invoice metadata (client ID, invoice number, timestamp, status) to a dedicated log sheet for auditability.

8. Slack Notification Node

Sends either success or error messages with invoice details to finance team Slack channel for transparency and alerts.

Error Handling, Robustness & Security

Error Handling & Retries

The workflow includes automatic retries—Make retries failed HTTP requests with exponential backoff 3 times before flagging errors. Conditional paths separate critical errors from non-blocking warnings.

Logging and Monitoring

All errors and success statuses are logged to Google Sheets for audit and troubleshooting. Additionally, Slack alerts notify finance immediately to take action.

Idempotency and Deduplication

Unique invoice numbers and Google Sheets logging ensure no duplicate invoices are sent even if the workflow is manually rerun.

Security Practices

• API keys and OAuth tokens stored securely in Make’s credential vault with least privileges.
• All PII data (client emails, addresses) handled over encrypted channels.
• Access restricted to designated finance and IT personnel via role-based permissions.
• Audit logs maintained for compliance.

Performance, Scaling & Extensibility

The automation is designed to scale with increasing invoice volume by:

• Using asynchronous batch processing to handle up to 500 clients monthly without delay.
• Webhook triggers for real-time invoice creation if needed, instead of batch polling.
• Modular workflow design separates data fetching, transformation, generation, and notification for easy updates.
• Capability to extend to multiple countries by adding locale-specific invoice templates and currency conversions.
• RestFlow’s managed hosting ensures reliable uptime and performance during growth.

Comparison Table 1: n8n vs Make vs Zapier for Invoice Automation

Platform	Cost	Pros	Cons
n8n	Free self-hosted / Paid cloud plans	Open source, flexible, advanced logic, low cost	Requires hosting/maintenance if self-hosted
Make	Starts from $9/mo scaling by operations	Visual builder, rich integrations, strong error handling	Learning curve, cost grows with volume
Zapier	Starts at $19.99/mo	User-friendly, many app integrations	Limited multi-step logic, higher cost for volume

Comparison Table 2: Webhooks vs Polling for Invoice Process

Method	Cost	Pros	Cons
Webhooks	Lower operational load	Real-time triggers, efficient resource use	Requires API support, more complex setup
Polling	Higher cost with frequent checks	Simple to implement	Delay in processing, inefficient resource usage

Comparison Table 3: Google Sheets vs Database for Invoice Data Storage

Storage Type	Cost	Pros	Cons
Google Sheets	Free up to limits	Easy access, integrates well with Make	Limited scalability and concurrent writes
Relational Database	Hosting costs apply	High scalability, robust data integrity	Requires management, complex setup

Results & Business Impact

Following the implementation of the automated invoicing workflow using Make and RestFlow services, the client observed significant improvements:

• Time saved: Over 25 hours per month previously spent on manual invoice generation were reclaimed by the finance team.
  Processing time reduced by approximately 70%. [Source: to be added]
• Error reduction: The invoicing error rate dropped from 8% to under 1%, greatly improving client satisfaction and reducing rework.
• Faster invoicing cycle: Invoices are now sent on schedule at the beginning of each month without delays, optimizing cash flow.
• Improved visibility: Real-time Slack notifications and Google Sheets logs allow management and finance teams to monitor progress and statuses instantly.
• Scalability: The system accommodates increased client volume without additional manual effort.

The workflow also boosted employee morale by eliminating repetitive manual tasks, allowing the finance team to focus on higher-value activities such as strategy and analysis.

For those eager to streamline their business processes, Create Your Free RestFlow Account to get started quickly.

Pilot Phase & Maintenance Disclaimer

This automation solution underwent a dedicated pilot phase during which real but controlled invoice data was processed. During this phase, minor bugs, edge cases, and client-specific peculiarities were uncovered and resolved to ensure reliability. Clients and RestFlow teams worked closely to tweak workflows for optimal accuracy.

Post-pilot, RestFlow provides ongoing managed hosting, monitoring, updates, and maintenance to guarantee smooth operation and quick adaptation to future business changes. This partnership ensures automation remains stable, secure, and continuously effective.

Conclusion

In summary, this automation success story illustrates how a logistics SME in Copenhagen relieved their finance and operations teams from the burden of spending more than 25 hours a month manually generating invoices by implementing a robust, scalable workflow using Make and RestFlow.

The integration of ERP APIs, Google Sheets, Gmail, and Slack into a seamless automated process produced significant time savings, improved accuracy, and enhanced operational visibility.

With RestFlow’s Automation-as-a-Service, customers receive a turnkey solution encompassing design, implementation, hosting, monitoring, and continuous maintenance—empowering organizations to focus on growth rather than routine tasks.

Don’t wait to optimize your invoicing process and other repetitive workflows. Explore the Automation Template Marketplace or create your free RestFlow account today to begin your automation journey.