Ask for payment up front, or give customs a declared value, with a proforma invoice that is clearly not a tax invoice.
A proforma invoice looks like an invoice but is a commitment, not a demand for payment that counts for tax. It is used to request an advance payment, to let a buyer arrange financing or an import licence, or to declare the value of goods to customs before the sale is final.
This page starts a Proforma invoice — its own document type with its own numbering (PF2026-001), the note “This is not a tax invoice.” and a payment QR code so the buyer can pay the advance straight away. It never counts towards your outstanding invoices. When the goods ship or the service is delivered, choose More → Create final invoice and every line is carried over.
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.
It is good practice to number it, but it must not use your tax-invoice sequence. Proformas here have their own series (PF2026-001, …), so your invoice numbers stay gap-free.
You can show VAT so the buyer knows the total, but the VAT becomes due only with the final tax invoice (or on receipt of an advance, depending on the country).