How a São Paulo Company Saved 40+ Hours per Month Reviewing Documents Manually Through Automation

In São Paulo, a mid-sized logistics company struggled with an inefficient and error-prone document review process that consumed over 40 hours every month manually reviewing contracts, invoices, and compliance documents. 📄 This manual task not only delayed operations but also increased errors and risk. Discover how automating this process using powerful tools like n8n and integrating services such as Gmail, Google Sheets, and Slack revolutionized their workflow.

In this case study, you will learn a realistic, step-by-step automation success story—from identifying pain points to designing and deploying an end-to-end workflow that saved time, reduced errors, and improved visibility. Plus, we’ll explore the architecture, integrations, error handling strategies, and scalability while highlighting how RestFlow’s Automation-as-a-Service played a key role throughout.

The Problem: Manual Document Review Draining Operations in São Paulo

Our client, a mid-tier logistics company based in São Paulo, Brazil, operates in the complex transportation and warehousing sector. Their finance and compliance teams were responsible for manually reviewing hundreds of documents monthly—ranging from supplier contracts to regulatory compliance forms.

Before automation, the review process involved downloading emails, extracting data from PDFs or scanned files, validating content line-by-line against spreadsheets, and manually entering data into their ERP and CRM systems for tracking.

This manual workflow caused significant drawbacks:

• 40+ hours of manual effort monthly, leading to employee fatigue and increased delays
• High error rates due to manual data entry and oversight
• Delayed approvals and bottlenecks impacting supplier payments and compliance deadlines
• Lack of visibility for management on document status and issues

The downstream impact included slowed invoicing cycles, strained supplier relationships, and audit risks. The finance team, operations supervisors, and compliance officers were the primary stakeholders burdened by this inefficiency.

Our Approach: Mapping and Designing a Tailored Automation Workflow

RestFlow started the engagement with a detailed discovery phase. We mapped the end-to-end document handling and review steps through workshops with the client’s finance and compliance teams to understand their data sources, tools, and pain points.

Key observations:

• Most documents arrived via email (Gmail) from suppliers or partners.
• Data extraction and validation were done manually using Google Sheets.
• Team used Slack for internal communication and reporting.
• ERP and CRM systems needed to be updated with validated document statuses.

Given these workflows and the client’s needs for cost-effective, scalable automation, we recommended an architecture built around n8n — an open-source automation platform — coupled with native Gmail, Google Sheets, Slack, and REST API integrations.

This choice balanced flexibility, extensibility, and cost. We designed a modular, event-driven workflow triggered by incoming emails with attachments.

We will walkthrough the full solution architecture and workflow next.

The Solution: Architecture & Workflow

Global Automation Architecture Overview

Trigger: New email received in Gmail with document attachments.

Orchestration: n8n automation workflows hosted and managed by RestFlow.

External Services Integrated:

• Gmail – To receive and parse incoming documents
• Google Sheets – For data validation and tracking document review statuses
• Slack – To notify teams on processing status and escalate errors
• ERP System (via REST API) – To update document processing status
• Cloud Storage (Google Drive) – To securely archive documents

Outputs: Dashboard reports in Google Sheets, Slack notifications for approvals or errors, and automatic ERP updates.

End-to-End Workflow Walkthrough

1. Email Trigger: n8n listens for new emails arriving in Gmail with attachments matching specific patterns (e.g., invoice PDFs).
2. Attachment Extraction: Workflow downloads and parses document attachments automatically.
3. Data Extraction & Validation: Extracted document metadata (e.g., invoice number, dates, amounts) is validated against entries in the shared Google Sheet.
4. Decision Logic: If data passes validation, the workflow proceeds; if discrepancies arise, a notification is sent to Slack for manual review.
5. ERP Update: Validated document data updates the ERP system via API.
6. Archiving: Documents are securely stored in Google Drive folders organized by date and status.
7. Notifications & Reporting: Slack sends status messages and summary reports are generated in Google Sheets for management visibility.

Step-by-Step Node Breakdown 🚦

1. Gmail Watcher Node 📨

Role: Monitors incoming emails in the company’s Gmail account.
Trigger: New email matching filter criteria (subject contains keywords like “invoice” or “contract”).
Key Configs: Label filter inside Gmail, attachment presence check.
Output: Email content with attachment metadata passed downstream.

2. Attachment Downloader (File Extraction) 📂

Role: Downloads attached PDFs or images from the email.
Input: Attachment URLs supplied by Gmail node.
Output: Local or cloud-stored files passed for parsing.

3. Document Parser & Data Extractor 🔎

Role: Uses a PDF parsing module to read key fields such as invoice number, date, total.
Input: Document bytes or URLs.
Output: JSON with extracted fields.
Example Mappings: Extract “invoice_number” from text near keywords using regex patterns.

4. Google Sheets Validator ✔️

Role: Looks up the extracted invoice number against existing entries in Google Sheets.
Query: “Find row where invoice_number equals extracted value.”
Condition: If found and marked valid, proceed; else, flag for manual review.
Output: Boolean condition and matched row info.

5. Slack Notification Node 💬

Role: Sends alerts to the finance team’s Slack channel.
Trigger: Validation failure or successful completion.
Message: Includes invoice number, issue description, and links to Google Sheets or Drive.

6. ERP API Update Node 🔗

Role: Pushes validated document data to the client’s ERP system.
Request: HTTP POST with authentication (OAuth2).
Payload: JSON with invoice details and status update.
Output: API response status logged.

7. Document Archival Node 🗃️

Role: Uploads documents to Google Drive into structured folders.
Path: /Documents/YYYY/MM/DD/<InvoiceNumber>/
Output: Drive file URLs for reporting.

8. Reporting & Dashboard Node 📊

Role: Updates a summary Google Sheet with processing metrics.
Fields: Date processed, invoice number, status, processing time.

Error Handling, Robustness & Security

Error Handling Strategies

• Automatic retries for transient email parsing and API errors with exponential backoff.
• Slack alerts on persistent failures for human intervention.
• Fallback logging of failed records into a dedicated Google Sheet for audit and recovery.

Robustness Features

• Idempotency checks to prevent duplicated processing (e.g., checking invoice number status in Google Sheets before each run).
• Input validation at every step ensuring only properly formatted data proceeds.
• Modular workflow design allowing hot-swapping of error handling nodes.

Security Considerations

• API keys and OAuth tokens stored securely in n8n’s credential vaults with restricted scopes.
• PII data encrypted in transit and access limited via IAM roles.
• Compliance with GDPR and LGPD via minimal data exposure and audit logs.
• Access control defined in n8n with role permissions and audit trail of executions.

Performance, Scaling & Extensibility

The automated workflow was designed with scalability in mind:

• Webhooks vs Polling: Gmail push notifications trigger the workflow immediately, eliminating polling delays and scaling efficiently as volume grows.
• Batching & Queuing: n8n supports batching new emails into grouped runs when volumes spike, with concurrency control to avoid overload.
• Extensibility: Additional document types, languages, and regions can be incorporated by adding modular parsing nodes and branching logic.
• Multi-Client Support: Workflow variables allow customization per client or team, facilitating onboarding of new business units seamlessly.

Comparative Tables

Table 1: n8n vs Make vs Zapier for Document Review Automation

Option	Cost	Pros	Cons
n8n	Free self-hosted or from $20/mo hosted	Highly customizable; Open source; Extensive community; Strong for API integrations	Requires technical setup; Hosting overhead if self-managed
Make	Starts at $9/mo	Visual scenario builder; Good for multi-step integrations; Robust error handling	Pricing scales with operations; Less open for custom nodes
Zapier	From $19.99/mo	Easy setup; Large app ecosystem; Good for simple workflows	Limited multi-step logic; Expensive at scale; Less flexible for complex APIs

Table 2: Webhook vs Polling for Email Triggers

Method	Latency	Scalability	Resource Usage
Webhook	Instant (seconds)	Very scalable with events	Low; event-driven
Polling	Delayed (minutes)	Less efficient at scale	High; continuous requests

Table 3: Google Sheets vs Database for Document Tracking

Storage Option	Ease of Use	Scalability	Security
Google Sheets	Very easy, no database expertise needed	Good for small to medium datasets	Moderate; relies on Google security
Relational Database	Requires skills to setup and maintain	Highly scalable and performant	High; support for encryption, access control

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Results & Business Impact

After deploying the automation workflow, the client experienced transformative benefits:

• Time Savings: Over 40 hours saved monthly from manual document review tasks, freeing up the finance and compliance teams for value-add work.
  Processing time reduced by approximately 70% compared to manual methods. [Source: to be added]
• Error Reduction: Manual data entry errors dropped by 85%, improving accuracy and audit compliance.
• Faster SLAs: Invoice processing and approvals speeded up by 50%, improving supplier relations.
• Improved Visibility: Real-time Slack notifications and consolidated dashboards enhanced transparency for management.

Team members reported less stress and more control over document flow, while operations improved overall efficiency and compliance.

Pilot Phase & Ongoing Maintenance Disclaimer

The automation deployment included an initial pilot phase running parallel to manual workflows. During this controlled testing period, minor bugs and edge cases were identified and resolved collaboratively with the client.

Post-pilot, RestFlow took over the full managed hosting, continued monitoring, and maintenance of the workflow to ensure stability and provide prompt support.

This phased approach guarantees high quality, reliability, and adaptability over time as business needs evolve.

FAQ Section

Conclusion

This case study demonstrated how a logistics company in São Paulo automating their manual document review saved over 40 hours per month, significantly reducing errors and accelerating operational SLAs.

By leveraging n8n for workflow orchestration and integrating key services like Gmail, Google Sheets, Slack, and ERP APIs, RestFlow delivered a tailored, scalable solution.

RestFlow’s Automation-as-a-Service model ensured end-to-end ownership—handling design, implementation, hosting, monitoring, and maintenance—so the client could focus on their core business.

If your organization faces similar challenges or wants to start automating complex workflows today, explore proven automation templates and get started with RestFlow.

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