Bill anything outside regular fees — uniforms, books, transport — and record payment.
Go to Invoices → New invoice. Fill the bill-to name (optionally link a student) and add line items — the sub-total updates live.

Optionally add a tax rate or a flat discount, then Create invoice. It's numbered automatically (INV-2026-0001).
Record a full or partial payment — the status moves Draft → Issued → Partial → Paid on its own. Print, save as PDF, or share on WhatsApp.