Mandatory invoice details: what an invoice must contain
8 July 2026 · 5 min read
An invoice is not a free-form message. The Value Added Tax Act sets out what a sales invoice must contain. When all the mandatory details are in order, the invoice is compliant, bookkeeping runs smoothly and the customer can deduct the VAT. Here is a clear list.
The mandatory invoice details
- The invoice date, that is the date of issue
- A running invoice number that uniquely identifies the invoice
- The seller's name, address and business ID (Y-tunnus)
- The seller's VAT identifier, if the sale is subject to VAT
- The buyer's name and address
- The quantity and type of the goods or services sold
- The delivery or performance date, if it differs from the invoice date
- The taxable amount per tax rate, that is the price without tax
- The tax rate, that is the VAT percentage
- The amount of tax payable in euros
- The total amount payable
VAT and tax rates
If the sale is subject to value added tax, the invoice shows the price without tax, the tax rate and the amount of tax separately. The standard tax rate is 25.5 percent, but some goods and services have a reduced rate. If the sale is tax-free or subject to reverse charge, that must be stated on the invoice.
Simplified invoice details
For small invoices of no more than 400 euros, and for example in retail, simplified invoice details may be used. A narrower set of information is then enough, but the seller's details, the date, the type of goods and the amount or basis of the tax must still be stated.
The most common mistakes
- The invoice number is missing or not running
- The business ID or VAT identifier is missing
- VAT has been calculated at the wrong rate
- The price without tax, the tax and the total do not add up
Invoicing software removes these mistakes: the mandatory fields are ready, VAT is calculated automatically and the invoice number runs by itself. Haimoo Invoice makes a proper invoice in minutes, so you don't have to remember every point by heart.