Working examples/Invoice reminders

Invoice reminders for a cleaning company

Cannon River Cleaning is made up for this example. The code is real and open: read it or run it.

The problem

Invoices go out, a few go quiet, and chasing them is awkward and easy to forget. Money sits unpaid for weeks.

What it does

• Reads the open-invoices export from QuickBooks, Wave, Square or a spreadsheet
• A friendly reminder 3, 7 and 14 days after the due date, on weekdays in business hours
• Partial payments shown plainly: “$100.00 of $180.00 left”
• At 30 days late, a note to the owner to step in, instead of a fourth email; a list of what’s owed every Monday

The messy parts it handles

• Dates written as 10/02/2026, Oct 25 2026 or 2026-10-20
• Money written as “$1,240.00”; names typed “Chen, Wei”
• An impossible due date (13/45/2026) or a missing email: passed to the owner, never guessed
• The week the clocks change: reminders still go out at 9 a.m.

The week, line by line

• 6usable invoices
• 2bad rows passed to the owner
• 6reminders
• 2late notes to the owner
• 2Monday lists
• 0weekend emails

Speed: A 5,000-row invoice export read and checked in 0.18 seconds on a desktop PC (npm run bench). A small business’s whole year fits in under a second.

For your business

Your invoicing tool’s own reminders are switched on first where they exist; this runs where they can’t, from the export you already have.

More examples

• Booking reminders for a dog groomerClients call to book while the groomer’s hands are full, so calls go unanswered, and the ones who do book sometimes forget and don’t show.
• Lead follow-up for a plumberA plumber on a job can’t answer email or the website form. Inquiries sit for hours, and the customer books the next plumber on Google.
• Review requests for a salonHappy clients mean to leave a review and forget, and asking in person feels awkward.