Library
Portfolio Builders · Chapter 3 of 5
Chapter 03

Project 2 — Invoice + WhatsApp Reminder
Reminder Flow

A tiny automation that recovers a shocking amount of unpaid invoices.

InvoicesWhatsAppCash Flow
A Handbook For Builders
Project 2 — Invoice + WhatsApp Reminder
Reminder Flow
Chapter 03
The Claude Code Handbook

A tiny automation that recovers a shocking amount of unpaid invoices.

Section

Client Problem

20% of invoices go past due. Two polite nudges recover most.

Section

Architecture

Cron → Sheets/DB → filter overdue → WhatsApp Cloud API → log reply.

Section

Build

Google Sheets node, filter expression, Loop Over Items, WhatsApp POST, back to Sheets.

Section

Delivery

Template message, tone-tuned in Roman Urdu / English.

Section

Pricing

$400 setup, or 5% of first month recovered.