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Billing glossary

What is an invoice?

Understand the document itself, then the billing work that surrounds it.

Format
glossary
Sections
04
Updated
10 Aug 2026
In brief

An invoice is a commercial document issued by a seller to a buyer that identifies supplied goods or services, the amount due and the payment terms. It usually includes a unique number, dates, party details, line items, taxes and total. An invoice records a payment request; it is not proof that payment has occurred.

01

What an invoice is for

An invoice gives both parties a structured record of what was billed and when payment is expected. It supports customer review, receivables tracking, tax documentation where applicable and later reconciliation with a payment.

  • Describe the supply
  • Show how the amount was calculated
  • State when and how payment is expected
  • Provide a reference for follow-up and matching

Put this into practice with Create an invoice step by step.

02

The fields an invoice usually contains

The exact legal fields depend on jurisdiction and transaction type. Most invoices identify the seller and buyer, invoice number, issue and due dates, descriptions, quantities, rates, taxes, total, currency and payment instructions.

Put this into practice with Use the invoice generator.

03

Invoice, receipt and proforma invoice

An invoice asks for payment. A receipt records that payment was received. A proforma invoice previews a proposed transaction before the final invoice. Keeping these purposes distinct makes commercial and accounting records easier to interpret.

Put this into practice with Explore invoice management.

04

The lifecycle after creation

A business invoice may still require outgoing approval, delivery, customer clarification, follow-up and payment matching. Billing operations software keeps those states connected instead of treating the PDF as the end of the process.

Common questions

Clear answers without the detour.

Is an invoice proof of payment?

No. An invoice records an amount requested from a buyer; it does not prove that money was received. A receipt, bank record or matched payment entry provides evidence of payment. Keep the invoice and payment relationship visible so finance can distinguish an open balance from an amount that has been paid but not yet matched.

Who issues an invoice?

The seller or service provider normally issues the invoice to the customer or buyer when the agreed billing event occurs. The issuing legal entity, document number, tax details and payment instructions should match the transaction. Where several entities operate in one group, each invoice should retain the correct entity-specific numbering and tax profile.

Can an invoice be changed after sending?

The correct treatment depends on the reason, transaction and jurisdiction. Preserve the sent record and use the required correction, credit note, cancellation or replacement process instead of silently editing it. This keeps the customer, receivables team and ledger aligned on which document is valid and why the amount or tax treatment changed.

What is an invoice number?

An invoice number is a unique reference used to identify, track and reconcile an invoice. It connects customer questions, collection actions and payments to the correct billing record. Numbering rules may be subject to local tax or record-keeping requirements, so use a documented sequence and keep entity-specific series distinct where necessary.

What happens after an invoice is sent?

The invoice may be delivered, viewed, questioned, disputed, become overdue, receive a payment or wait for that payment to be matched. A billing operation keeps those states, owners and next actions connected to the document. The PDF is the customer-facing output; the operational record continues until the balance is resolved.