Jayson Bautista.

Invoice follow-up.

A scheduled invoice workflow with overdue checks, generated messages and a follow-up log.

  • n8n
  • Google Sheets
  • Groq
  • Gmail

Personal project · Source-backed architecture

DisciplineAutomation Engineering
StatusDocumented architecture
My rolePersonal automation project; workflow documentation and technical explanation

The problem explored

Connecting overdue invoice checks with a follow-up message and a traceable log.

A scheduled invoice workflow with overdue checks, generated messages and a follow-up log. The supplied diagrams document the configured connections, rather than verified production outcomes.

Authentic cropped source architecture from my Invoice follow-up n8n project
Invoice follow-upEditor whitespace removed; original nodes preserved
Full source

Scroll sideways to inspect the diagram. Zoom enlarges labels; Reset zoom restores this preview.

Architecture summary · read alongside the source

  1. Read invoice records
  2. Check overdue status
  3. Prepare a message
  4. Send & record

Inside the processing logic

Read invoice records

  • A Schedule Trigger starts the visible workflow.
  • ReadConfig and Get All Invoices read Google Sheets data.
  • A Filter node appears before the overdue calculation.

Check overdue status

  • Calculate Days Overdue is a code node.
  • An If node follows the calculation.
  • Exact overdue thresholds and scheduling settings are not visible.

Prepare a message

  • The selected branch reaches an AI Invoice Agent.
  • The agent is connected to a Groq chat model.
  • The screenshot does not reveal the message prompt or collection policy.

Send & record

  • A Gmail Send Invoice node follows the AI agent.
  • Update Invoice Row writes back to Google Sheets.
  • Log to Follow-up Sheet records the follow-up step.

Step through the explanation

Dennice, an original illustrated robot guide, walks through the diagram. Start with Next, or choose autoplay. Captions and a full transcript are included; sound is optional.

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Source evidence

These are the supplied local files used to write this explanation. Node labels and connections are visible; exported workflow JSON and execution logs were not supplied.

Invoice follow-up source diagram 1
Source: automation3/1.png. Open original image

Visible outputs

An invoice email, an updated invoice row and a follow-up sheet entry.

These outputs are represented by nodes in the source. Delivery success and business results require execution evidence.

What this case study does—and doesn't—verify

The diagram supports the visible invoice-processing sequence. Successful delivery, payments recovered and time saved are not evidenced. Recipient checks and approved reminder wording need verification before use.

Next validation steps

Before operational use, I would inspect the workflow export, confirm credentials and permissions, test representative inputs and error paths, and review the outgoing messages with the intended user. These are proposed checks, not completed workflow execution tests.

Next: WhatsApp support routing

Let’s make
something work.

Have a development role, an automation idea or a website project in mind? I’d like to hear about it.

Jayson Bautista · Automation Developer & Web Developer