Invoicing is one of those things that looks simple until you've had a client dispute a charge, miss a payment, or ask for details you forgot to include. A well-structured invoice protects you, sets clear expectations, and signals professionalism.
What Every Invoice Must Include
No matter the project size, a complete invoice should have:
- Your full name or business name and contact information
- Client's name and billing address
- Invoice number — a unique identifier (e.g. INV-001)
- Invoice date and due date
- Itemised list of services with quantities and unit prices
- Subtotal, VAT/tax (if applicable), and total
- Payment details — bank account (IBAN/BIC for EU) or payment link
Missing any of these can delay payment or create legal ambiguity in disputes.
Common Mistakes That Delay Payment
1. Vague line items
"Consulting — €1,200" tells the client nothing. They may question it.
Use specific descriptions: "UX design for mobile app onboarding flow — 12 hours × €100/hour".
2. Wrong payment details
Double-check your IBAN every time. One digit off and the transfer bounces or goes to the wrong account.
3. No due date
Without a due date, "payment within 30 days" is ambiguous. Add an explicit date: "Due: 20 May 2026".
4. Not following up
Most late payments are simply forgotten. Send a polite reminder 3 days before due date and again on the day it's due. Automated reminders remove the awkwardness.
Invoice Numbering Best Practices
Keep a consistent format. Common patterns:
INV-001,INV-002— simple sequential2026-001,2026-002— year-prefixed (restarts each year)CLIENT-001— per-client numbering
Sequential, predictable numbering also looks more professional to accountants and finance departments.
EU-Specific Requirements
If you operate in the EU and your client is a business (B2B), you likely need to include:
- Your VAT number (if VAT-registered)
- Client's VAT number (for intra-EU transactions)
- Currency and applicable VAT rate
When invoicing clients in other EU countries, the reverse charge mechanism often applies — the invoice should state "VAT: Reverse charge" and include both VAT numbers.
Sending the Invoice
PDF format is the standard. It prevents accidental editing, looks the same on any device, and is easy to archive.
Send by email with a short note:
"Hi [Name], please find the invoice for [project] attached. Due date is [date]. Let me know if you have any questions."
Getting Paid Faster
- Invoice immediately after completing work — don't wait
- Shorter payment terms (14 days instead of 30) are increasingly common and accepted
- Add a payment link when possible — reduces friction
- Follow up consistently — a 3-day reminder, an on-due reminder, a 7-day overdue notice
Invify automates the follow-up reminders so you never have to chase awkwardly.
Ready to send your first invoice? It takes under 60 seconds — no signup required.