How I Built a Client Invoice System with Claude Code (Opus 5) in Under 2 Hours — Full Tutorial
Last Updated on August 24, 2026 by Editorial Team
Author(s): Felix Kebaya
Originally published on Towards AI.
How I Built a Client Invoice System with Claude Code (Opus 5) in Under 2 Hours — Full Tutorial
I needed an invoice system for my freelance work. I was using Google Docs templates… copying a doc, editing the client name, changing the amounts, and exporting as PDF.
The rest of the article walks through building a production-ready freelance invoice system using Claude Code (Opus 5): first defining the app features (Supabase-authenticated client and invoice management, draft/sent/paid/overdue invoice lists, PDF export, and a dashboard), then showing Step 1 (set up Supabase tables and RLS policies), Step 2 (copy a full spec into Claude Code), and Step 3 (results—six features delivered via one prompt, plus a follow-up prompt to fix invoice number formatting). It then covers Step 4 refinement to make the UI and PDF professional without breaking Supabase logic, and Step 5 deployment to Vercel in minutes. The author concludes with total time/cost (under ~2 hours; essentially $0 if using free tiers plus an existing Claude Pro subscription) and argues that this is a marketable process: the same workflow can be repeated for other client-paid internal tools, demonstrating how quickly AI coding agents can produce shippable apps.
Read the full blog for free on Medium.
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