How I Built an Automated WhatsApp Invoice System for My Client in 3 Hours

Last week, a CA firm in Jaipur reached out to me with a painfully familiar problem: their accountant was manually creating invoices in Excel, converting them to PDF, and sending them on WhatsApp — one by one — to 200+ clients every month. Time spent? About 3 full working days. Every. Single. Month. I built them an automated system in 3 hours flat. Here's exactly how. The Problem The firm's workflow looked like this: Open Excel template Fill in client name, GSTIN, amounts, due dates Save as PDF Open WhatsApp Web Search for the client Attach PDF, type a message, hit send Repeat 200 times The accountant was burning ~24 hours/month on this. At ₹300/hour, that's ₹7,200/month — or ₹86,400/year — just on invoice delivery. The Solution: Python + WhatsApp Business API I broke the automation into 3 parts: Invoice generation from a Google Sheet PDF creation using a template WhatsApp delivery via the Business API Part 1: Pull Data from Google Sheets First, I set up a Google Sheet as the single sou