Instalment and Payment Plan Tracker

Instalment and Payment Plan Tracker is an offline app: one HTML file in a zip that opens by double-click, with no installation, internet or subscription.

The problem it removes: Selling on instalments, whether furniture, equipment, fit-out, tuition, memberships or a car repair, means a promise of money over months to a list of customers. It usually lives in a notebook or a spreadsheet nobody updates: who paid the third instalment, who is two behind, what was agreed when the customer asked for more time. Collections are chased late or not at all, and the owner cannot say what cash is coming next month.

What is inside:

• A plan per customer: price, deposit, number of instalments, frequency and first due date; the schedule is built for you and any rounding remainder goes into the last instalment
• Record a payment: it is applied to the oldest unpaid instalment first, shows what it covered, and you print a numbered receipt; an overpayment is shown, and a payment can be deleted to reverse it
• A Chase list: everything overdue or due within the days you set, oldest first, with a ready WhatsApp or SMS reminder whose wording you edit
• Restructure when a customer asks for more time: replace the unpaid instalments with a new schedule, or change one instalment's date or amount; the history records every change
• Add an extra instalment or charge (for a late fee that your contract allows)
• Expected collections: what the schedules say you will receive in each of the next 12 weeks
• Cancel and reactivate a plan; printable schedule for the customer
• Example data, CSV export, JSON backup and restore

In the zip: index.html (the app), README.txt (quick start, how it calculates, limits) and EXAMPLE-DATA with a made-up example you can restore. Start in 10 minutes: open index.html, press Load example data, look around, press Clear everything and enter your own settings.

Rules are settings, not built in. Grace days before an instalment counts as overdue, the days that count as due soon and the reminder wording are settings. The app charges no interest and no late fee by itself.

Who it is for: furniture and equipment sellers, fit-out and maintenance contractors, schools and clubs, and workshops that agree payment plans with customers.

What it is NOT: a lending or financing tool: it does not calculate interest or financing charges, and instalments are equal parts of the balance unless you change them. It does not collect money. A printed schedule is a record of what was agreed, not a legal contract: ask your lawyer about your terms. Post-dated cheques held against a plan can be tracked in PDC Cheque Register. Invoice Chase Desk works from invoices; this works from an agreed schedule per customer.

Your data stays on this device in your browser. Back it up with Export; clearing browser data loses it otherwise.

Verified by us: 95 scripted checks through the real screens in Chromium, run at 1280 px and at 375 px, including independent Python derivation of each instalment's status, paid, balance and the 12-week forecast from the example plans, the schedule rounding, payment application, overpayment, payment deletion, a restructure, an edited instalment with a mismatch warning, cancel and reactivate, the chase list, grace days, settings, CSV export and backup. The schedule and a receipt were rendered to PDF in Chromium and looked at. Not tested in Firefox or Safari (neither could be launched in our test environment), in Edge, on a real phone, on a real printer, or with real bank or accounting exports; layout checked at 375 px and 1280 px.