An Informal Invoice is commonly used in Swiss business operations when a simplified billing format is appropriate while still maintaining legal compliance. This document type is particularly useful for small businesses, freelancers, and service providers who need to bill clients without the complexity of a formal commercial invoice. Under Swiss law, particularly the Code of Obligations and VAT regulations, an Informal Invoice must still include certain essential elements such as party identification, service/product details, and payment terms. The document serves as official proof of a business transaction and can be used for accounting and tax purposes, though it takes a more streamlined approach compared to formal invoices. It's especially suitable for one-time services, smaller transactions, or ongoing business relationships where a more casual but still professional approach is appropriate.

1. Invoice Header: Contains invoice number, date, and clear marking as 'Invoice'

2. Seller Information: Full business name, address, contact details, and any registration numbers

3. Buyer Information: Client's full name, address, and any relevant reference numbers

4. Service/Product Details: Itemized list of products or services, quantities, unit prices, and descriptions

5. Payment Information: Total amount, payment terms, due date, and bank account details

6. VAT Information: VAT number (if applicable) and VAT amount breakdown