How to Write a Professional Invoice (What to Include)

How to Write a Professional Invoice (What to Include)

October 20, 2026

A clear invoice gets paid faster and avoids disputes. It is also a legal and tax document in most countries, so the details matter.

What every invoice should contain

  • The word "Invoice" and a unique invoice number.
  • Your details: business name, address, contact information and, where required, your tax or VAT number.
  • Your client's details: name and billing address.
  • Issue date and due date, with payment terms such as "Net 14" (due 14 days after issue).
  • A description of each item or service, with quantity, unit price and line total.
  • Subtotal, taxes and total due, shown separately so the client can see what tax applies.
  • Payment instructions: bank details or payment link, and any late-fee policy.

Numbering

Use a simple, sequential system such as INV-0001, INV-0002. Never reuse a number; accountants and tax authorities expect a continuous sequence.

Create one in minutes

The Invoice Generator lets you fill in the fields above and download a clean PDF. UK users can also look at Invoice Templates (UK). If a client asks for a price before work begins, the Quotation Generator produces a quote in the same style, and after payment you can issue a Receipt as proof.

Invoice, quote or receipt?

  • Quotation: an offer of a price, not a request for payment.
  • Invoice: a request for payment for work done or goods supplied.
  • Receipt: confirmation that payment was received.

Tips for getting paid on time

  • Send the invoice as soon as the work is delivered.
  • State the due date clearly and make it easy to pay.
  • Follow up politely a few days before and after the due date.
  • Keep copies of everything for your records and for tax time.

Tax rules differ by country. If you are unsure what must appear on your invoices, check with your tax authority or an accountant.

Frequently asked questions

Do I need to be registered to send an invoice?

Any business or freelancer can issue invoices, but tax registration requirements depend on your country and income level. Ask your tax authority if you are unsure.

What payment terms should I use?

Common terms are due on receipt, Net 7, Net 14 and Net 30. Shorter terms improve cash flow; choose what is normal in your industry and agree it in advance.

Can I charge late fees?

Only if you stated the fee on the invoice or in a prior agreement, and where local law allows it.

How long should I keep invoices?

Tax authorities usually require records for several years. Check your local rule and keep digital copies backed up.

Key takeaways

  • Number invoices sequentially and never reuse numbers.
  • Show tax separately.
  • Include clear payment instructions and due dates.