How to Make an Invoice (With Template and Worked Example)

By Ricardo Lau Cooper, Senior Financial Data Analyst · LinkedIn

A good invoice gets you paid faster and keeps your records clean for tax season. This guide covers what every invoice must include, a full worked example with tax and totals, and a free invoice template that does the calculations for you.

What must an invoice include?

Exact legal requirements vary by country, but every professional invoice should contain these elements. Missing any of them is the most common reason invoices get questioned or paid late.

• Your name or business name and contact details
• Client name and contact details
• A unique invoice number (sequential, e.g. 2026-001)
• Issue date and payment due date
• Line items: description, quantity, unit price
• Subtotal, tax rate and amount, and total due
• Payment methods and terms (e.g. bank transfer, 30 days)

Worked example: invoice with tax

Suppose you are a designer billing a client for a branding project. Your invoice has two line items and a 16% tax rate:

• Logo design — 1 × $800 = $800
• Brand guidelines document — 1 × $400 = $400
• Subtotal: $800 + $400 = $1,200
• Tax (16%): $1,200 × 0.16 = $192
• Total due: $1,200 + $192 = $1,392

With a due date 30 days after issue, the client must pay $1,392 by that date. A clear due date and invoice number make it easy for both sides to track the payment — and easy for you to follow up if it is late.

Tips to get paid faster

• Send the invoice the same day you deliver the work, not at month end.
• State a concrete due date ('Due March 15') instead of vague terms.
• Offer a simple payment method — the fewer steps, the faster the payment.
• Number invoices sequentially and keep a copy of every one for taxes.
• Follow up politely the day after the due date — most late payments are oversight, not refusal.

Common invoicing mistakes

• Forgetting the tax line or applying the wrong rate for your country.
• Reusing the same invoice number, which confuses your records and your client's.
• Describing work vaguely ('services') instead of itemizing what was delivered.
• Not agreeing on payment terms in writing before starting the work.