If you run a one-person consultancy, late invoices cost you twice: once in cash flow, and again in the 20 awkward minutes it takes to write a reminder that's firm but doesn't burn the relationship. This tutorial builds a Claude Code skill that does the awkward part: it reads a plain-text invoice list, works out who is overdue, and drafts the right reminder for how late each one is. You still press send. You need Claude Code installed ( https://code.claude.com/docs/en/setup ). 1....