Why are correct invoice details important?
An invoice is more than just a payment request. It serves as proof for accounting, VAT returns, and tax purposes.
Consequences of incorrect invoices:
• VAT reclaim rejected: Without valid invoice, no VAT deduction
• Accounting issues: Non-compliant invoices are not valid proof
• Tax fines: Serious infringements can lead to penalties
• Customer disputes: Incomplete invoices cause confusion
• Payment delays: Incorrect invoices are often returned for correction
Fortunately, it's easy to comply with all requirements with the right tools. Our free invoice maker automatically ensures all required fields are present.
Complete checklist: Required invoice data
Below is a complete list of data that must be on every invoice according to most tax regulations:
1. Invoice number
• Unique and sequential numbering
• Cannot contain gaps
• May contain letters and numbers (e.g., INV-2025-0001)
2. Invoice date
• Date on which the invoice is issued
• Cannot be in the future
3. Seller details
• Full company name
• Full address (street, number, postal code, city)
• Country (for international invoices)
4. VAT identification number seller
• Your VAT number
• Format varies by country
• Mandatory for VAT-liable entrepreneurs
5. Business registration number
• Registration number with the chamber of commerce
• Format varies by country
Customer details and description
6. Buyer details
• Full name or company name
• Full address
• For B2B invoices: customer's VAT number
7. Description of goods/services
• Clear, specific description
• Not 'Services' but 'Website development January 2025'
• Specify quantity, unit, and unit price
8. Date of supply
• When was the service provided or goods delivered?
• May be the same as invoice date
• For services: period of service
9. Quantity and unit prices
• Number of units per line
• Price per unit excluding VAT
• Total per line
With our invoice creator, you add all these details step by step.
VAT information on your invoice
10. VAT rate per line
• Applicable rate (e.g., 0%, 6%, 9%, 21%)
• Different rates on separate lines
• VAT exemption requires specific statement
11. VAT amount per line
• Calculated: amount excl. VAT × VAT rate
• Clearly stated per line
12. Total amounts
• Total excluding VAT
• Total VAT (split by rate if applicable)
• Total including VAT
When NOT to charge VAT:
• Reverse charge mechanism (B2B within EU): state 'VAT reverse-charged'
• Export outside EU: state 'VAT 0% export'
• Small business exemption: state 'VAT exemption small business scheme'
Use our VAT calculator for correct VAT calculations.
Payment information
Besides required data, it's wise to include clear payment information:
13. IBAN (bank account number)
• Correct IBAN format
• Validate before including on invoice
• Optionally include BIC for international
14. Payment term
• Due within X days
• Or specific due date
• Default is often 30 days
15. Payment reference
• Helps with payment processing
• Can be invoice number
Check your IBAN first with our free IBAN validator to prevent payment problems.
Special situations
In some situations, additional data or other rules apply:
Simplified invoices (small amounts):
For retail receipts and small amounts, a simplified invoice is sufficient with fewer details. Requirements vary by jurisdiction.
International invoices (EU):
For B2B within the EU:
• Include both VAT numbers
• State 'Reverse charge' for VAT reverse-charge
• Include EU country codes
Credit notes:
When issuing a credit note:
• Reference to original invoice (number and date)
• Reason for credit
• Negative amounts or clearly stated as credit
Use our credit note creator for correct credit notes.
E-invoicing (UBL):
For digital invoicing in UBL format, additional technical requirements apply. Our tools can export to UBL: PDF to UBL converter.
Common invoice mistakes
These are the most common mistakes we encounter:
1. Missing invoice number
Every invoice needs a unique, sequential number.
2. Incorrect VAT calculation
Calculating VAT on the total instead of per line, or using wrong rates.
3. Vague descriptions
'Services February' says nothing. Be specific: 'Website maintenance February 2025, 8 hours @ €75'.
4. Missing VAT number
Especially for B2B invoices, this is essential for VAT reclaim.
5. Wrong IBAN
Typos in your bank account lead to failed payments.
6. No delivery date
The date of delivery or service must be stated separately.
7. Incomplete addresses
Missing city, postal code, or country.
Frequently asked questions
Must VAT always be on an invoice?
Yes, unless you're exempt or the reverse charge mechanism applies. In those cases, state the reason for exemption.
Can I invoice without VAT number?
Yes, if you operate below the VAT registration threshold, but you cannot charge VAT and customers cannot reclaim VAT.
How long should I keep invoices?
Typically a minimum of 7 years. Digital storage is allowed.
Can I modify an invoice after sending?
No. Create a credit note for the original and optionally a new correct invoice.
Is a digital invoice legally valid?
Yes, digital invoices have the same legal status as paper invoices, provided they meet all requirements.
What about invoice templates?
Our free tools use professional templates that include all required fields automatically.
Free invoice tools
Winkel Factuur offers free tools to help you create correct, compliant invoices:
📝 Invoice Creator
Create professional invoices with all required fields. Automatic VAT calculation, export to PDF and UBL.
📄 Credit Note Creator
Create credit notes for returns or corrections. Automatically linked to original invoice.
🔢 VAT Calculator
Quickly calculate VAT amounts with different rates.
🏦 IBAN Validator
Check IBAN numbers for validity before using on invoices.
📤 PDF to UBL Converter
Convert PDF invoices to UBL format for e-invoicing.
All tools are free, no registration required, and your data is not stored.