What Is an Invoice?

For: business owners who want to understand the document they are sending.

An invoice is a formal request for payment. You send it to a customer after delivering goods or services, and it states what you delivered, how much the customer owes, and when you expect payment.

What makes an invoice valid

Most tax authorities require a few core elements:

• A unique, sequential invoice number
• Your business name and address
• Your customer's name and address
• The date the invoice was issued
• A description of what was delivered
• The amount owed, including tax breakdown
• Payment terms (when payment is due)

InvoiceScript fills in all of these when you finalize an invoice. The invoice number comes from your configured numbering sequence, the tax breakdown is calculated from per-line tax rates, and the customer and company details come from your records.

Invoice vs. other documents

Invoice vs. receipt. An invoice requests payment. A receipt confirms payment was received. InvoiceScript creates invoices. When you record a payment, the invoice status changes to paid, but InvoiceScript does not generate a separate receipt document.

Invoice vs. quote. A quote proposes a price before work begins. It is non-binding. An invoice requests payment for work already delivered. InvoiceScript supports both, each with its own numbering sequence.

Invoice vs. pro-forma. A pro-forma invoice looks like an invoice but has no legal weight. It is a prepayment request or a preview of what the final invoice will look like. InvoiceScript supports pro-formas as a separate document type.

Invoice vs. credit note. A credit note reverses or reduces an invoice. If you overcharged a customer or need to correct a mistake after finalization, you issue a credit note against the original invoice. See Quotes, Invoices, and Credit Notes.

Worked example

Mira Holst runs Northwind Studio, a small design studio. She finishes a website design project for Acme Hardware and creates an invoice:

• Invoice number: NW-2026-0003
• Issue date: 15 May 2026
• Due date: 14 June 2026 (30-day payment terms)
• Line items: 16 hours of website design at €125/hour, 4 hours of frontend development at €135/hour
• Subtotal: €2,540.00
• VAT 21%: €533.40
• Total: €3,073.40

She finalizes the invoice, which locks the number and generates the PDF. She sends it by email. The PDF includes an EPC QR code because she has a EUR bank account with IBAN configured. Acme Hardware's bookkeeper scans the QR code with their banking app and pays in two minutes.

What InvoiceScript does not do

InvoiceScript creates invoices and tracks payments. It does not file tax returns, calculate your tax obligations across jurisdictions, or replace your accountant. It gives you a clean, structured invoice you can hand to your accountant at the end of the quarter.

Related pages

• Quotes, Invoices, and Credit Notes
• Why Invoice Numbers Must Be Sequential
• How Payments Work