No easy way to track freelance client payments

Problem Description

I work with 8+ clients every month as a freelance developer. Currently using a messy Google Sheet to track: - Who paid vs who didn't - Payment due dates - Which invoices are overdue - Sending payment reminders The problem: I have to manually check my bank account, update the sheet, set calendar reminders, and copy-paste email templates. Takes 2+ hours per month. QuickBooks and FreshBooks are too expensive ($40+/month) and have features I don't need. Wave is free but clunky and slow. I just need: Upload invoice → Track status → Get reminded when overdue. That's it.