Nowadays, when everyone can use online payments with a QR code, using mobile phones or smart watches, there are still many entrepreneurs who issue their invoices and tax documents manually, for example in Excel.

Whether you're starting a business or getting into invoices for the first time at work, it's good to know the ins and outs.

Invoicing comes with a lot of rules to follow. And invoicing itself often takes a lot of time, too, and now and then a mistake can happen that attracts a financial audit.