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How to write an invoice

An invoice records a supply and requests or documents payment. This guide covers the fields most business invoices use, then shows how to identify the parties, describe the work, verify tax treatment, state the amount due, send the document and retain your records. Legal requirements vary by country, tax status and transaction.

6-minute read · 27/08/2026

Which fields should an invoice include?

There is no universal invoice checklist. The supplier’s country, tax registration, customer, type of supply and timing can change the required fields and format. Start with the common business details below, then check the rules for the transaction. Quotes, invoices and receipts also serve different purposes:

DocumentTypical timingPurpose
Quote or estimateBefore an order or workProposes scope and price; its legal effect depends on the terms and acceptance
InvoiceAt the required billing pointRecords the supply and requests or documents payment
ReceiptAfter paymentConfirms that payment was received
Document label
Identify it clearly as an invoice so it is not confused with a quote, order or receipt.
Supplier details
The legal or trading name, required address and contact details, plus registration identifiers that apply.
Customer details
The name and address required for the person or entity being billed.
Invoice identifier
A unique reference; some tax systems require a sequential number from one or more series.
Relevant dates
Usually the issue date, supply or tax-point date, and an agreed or stated due date.
Supply details
A clear description, quantity or extent, unit price and line amount where applicable.
Totals and tax
Currency, net amount, discounts, tax treatment and final amount, as the rules require.
Payment terms
The due date and accepted method, with bank details or a payment URL only when appropriate.

Step 1: Add your details

Identify the legal supplier. Use the registered business name or the personal and trading names required for your business structure, together with the applicable address and contact details. A logo is optional and does not replace the legal identity.

Show a company, VAT, GST or other registration number only when the law or transaction calls for it. Do not publish a personal tax identifier merely because the template has a field. Check which identifier the customer needs and whether it is appropriate to place on a document they will store or forward.

Step 2: Add the client

Use the name and billing address of the person or legal entity that bought the goods or services. Confirm the billing contact and any purchase order, buyer reference or contract number the customer requires. For some domestic or cross-border tax treatments, the customer’s tax identifier is mandatory; in other cases it is unnecessary. Validate it where the applicable rules require validation.

Step 3: Give it a unique number and dates

Give the invoice a unique identifier. Tax rules in many jurisdictions require a sequential number based on one or more series, but a blanket no-gaps rule does not apply everywhere. A scheme such as 2026-001, 2026-002 is easy to reconcile. Never reuse a number; retain the audit trail for cancelled, voided or corrected documents as required.

Add the issue date and the supply or tax-point date when required. State the due date that follows the contract and local payment rules. A calendar date is clearer than “Net 30” on its own.

Step 4: Itemise the work

List each product or service with a description specific enough to identify the supply. Add the quantity or extent, unit price and line amount where they apply. “Homepage redesign - 12 hours” is easier to approve than “design work”. Show discounts and additions clearly, then reconcile the lines to the subtotal.

A free invoice generator can calculate line totals and the tax rate you enter. It cannot decide whether the supply is taxable, exempt, zero-rated or subject to reverse charge, so verify that treatment separately.

Step 5: Add tax

Determine the tax treatment before calculating the total. Registration alone does not mean every supply uses the standard rate. The result may be standard-rated, reduced, zero-rated, exempt, outside scope, reverse charged or covered by a special scheme. Sales-tax obligations can also depend on location, nexus, product and customer.

Show the registration numbers, taxable amounts, rates, tax amounts and required legal notes for the treatment that applies. A reverse-charge transaction does not use one universal set of fields or one generic zero-tax label. If you are unregistered, do not charge or present yourself as registered, but check whether another reporting or buyer-accounting rule still affects the invoice.

Step 6: Show the total and payment terms

Show the final amount prominently and identify the currency. Recheck the subtotal, discounts, tax and rounding against the line amounts. State the contractual due date and accepted payment method. Include bank details or a payment URL only after checking that they belong to the supplier and are safe to share.

Mention late interest or recovery fees only when the contract and applicable law allow them. An invoice cannot create a new penalty after the agreement was made. Keep the payment wording short and consistent with the underlying contract.

Step 7: Send and track

Send the invoice through the channel and in the format the customer and jurisdiction accept. A PDF is common, but it does not replace a required structured e-invoice or tax-authority submission. Confirm the recipient, especially before exposing bank details or personal data.

Record when the invoice was sent, delivered, due, paid, cancelled or corrected. Retain the invoice and supporting records in their required original form for the applicable period. If payment is late, follow the contract and local reminder, interest and debt-recovery rules.

Frequently asked questions

What has to be on an invoice?

There is no universal minimum. Common fields identify the supplier and customer, the invoice, relevant dates, the goods or services, amounts, currency and payment terms. Tax invoices may also need registration numbers, a sequential number, supply date, taxable amounts, rates, tax amounts and specific notes. Check the rules for the transaction.

How do I number invoices?

Use a unique identifier that never repeats. Many tax systems require a sequential number from one or more series, such as 2026-001 and 2026-002. Do not assume every jurisdiction has the same no-gaps rule. Keep the required audit trail for voided, cancelled and corrected invoices.

Do I need to charge tax on my invoice?

Registration is only one part of the decision. The supplier, customer, location, product or service and any special scheme determine whether the supply is taxable and which rate or note applies. Do not charge tax or display a registration number you are not entitled to use. Confirm cross-border and reverse-charge treatment before issuing the invoice.

What payment terms should I set?

Use the terms agreed with the customer and allowed by local law. State a calendar due date, accepted method and verified payment instructions. Include late interest or recovery fees only when the agreement and law support them.

What is the difference between an invoice and a receipt?

An invoice records what is billed and often requests payment. It can be issued before, at, or after payment depending on the transaction and applicable rules. A receipt records money received. The same transaction can produce both documents, but their order and required contents depend on the circumstances.

How do I send an invoice?

Use the recipient, channel and format agreed with the customer and accepted by the jurisdiction. A PDF may be suitable, but some transactions require a structured e-invoice or tax-authority channel. Keep the original record and follow the applicable reminder process if payment is late.

Create a professional invoice free

FreeBillGen provides itemised lines, calculated totals, configurable tax and a PDF draft with invoice labels in multiple selectable language options, with no card required. Confirm the invoice number, tax treatment, required fields and delivery format before issue; guidance may remain in English until reviewed.

Create an invoice

Sources

Reviewed and maintained by the FreeBillGen team.

General information, not tax or legal advice. Rules vary by country and change; verify for your jurisdiction.