Invoice numbers, due dates and tax

All of these live in Settings → Invoicing and apply to invoices you create after changing them.

• Number prefix and Next number make the invoice number, such as INV-0142. A number is never used twice, even if you delete the invoice that had it.
• Currency is the one new invoices start in.
• Payment terms set the due date: on receipt, 14 days or 30 days after the issue date.
• Tax name and Tax rate are what the tax switch on a new invoice adds.
• Payment instructions are printed in a tinted block near the bottom of every invoice, and Footer message at the foot.

For bank details, PayPal, Wise and the rest, see Tell clients how to pay you.