Order from suppliers with a clear, numbered purchase order they can confirm and invoice against.
Enter the supplier, the items with quantities and agreed prices, and the delivery date you need. The PO gets its own number (PO2026-001) — give that number to your supplier so it appears on their invoice, which makes matching and bookkeeping easy.
There is no account and no server behind this invoice generator. Your business details, clients, products and invoices are stored in your browser's own database (IndexedDB) and never uploaded. The PDF is built on your device. The only request the app ever makes on its own is optional: if you click Use ECB rate on a foreign-currency invoice, it asks the European Central Bank for that day's reference rate — sending just the two currency codes and the date. That also means nobody else has a copy — download a backup from Settings → Backup now and then, and keep it with your accounting files. Nothing is locked in: every PDF carries its own data, the backup format is documented, and you can download an offline copy of the whole app.
Once the supplier accepts it, a PO usually forms a contract for the goods or services at the stated price. The exact rules depend on your country and terms.
Yes — the counterparty is saved like a client when you issue, so you can pick them next time.