Every customer gets a running ledger — paid, due and overdue — with due-date alerts and a reminder ready to send.
The register works until it doesn’t: a payment goes unrecorded, an installment is forgotten, and a month later nobody agrees on the balance. TameerBook keeps each customer’s khata live, so the figure is never in doubt.
Set an installment plan, record part-payments as they come, and the app tells you what is due. The WhatsApp reminder is written for you; send it in one tap. Customers with an email address get reminders by email automatically.