Chronos Invoicing

Every small team I talked to had the same setup: an invoice template in Google Docs, a spreadsheet tracking who had paid, and a calendar reminder to nag late clients by hand. It worked, technically, the way duct tape technically holds something together.

What none of them had was one place that actually knew the state of their business: which invoices were sent, which were overdue, which client always pays on day 45 instead of day 30. That context lived in someone's head, not in a system.

So Chronos Invoicing is the thing I wanted to hand them instead. Real clients, real invoices, real payment tracking, PDFs that just work, and reminders that go out without anyone remembering to send them. Recurring billing for the clients who pay every month. A dashboard that actually answers "how are we doing" instead of making you go add it up yourself.

Slim 4 (PHP) API and a React + TypeScript SPA, built across 12 stages: auth, clients, invoices, payments, PDF generation, email delivery and reminders, recurring invoices, a dashboard, quotes, a media library, and a full admin panel. PDFs render on the fly and stream straight to the browser rather than being pre-generated and stored.

Recurring billing and reminder logic look simple until you actually build them. 'Send this again next month' quietly touches invoice numbering, payment status, and email delivery all at once, so most of the real debugging time went into edge cases in that loop rather than the initial build.