How to invoice travel and supply-related expenses for a service/product:
You can incorporate the expenses directly into the service/product you are selling or invoice them separately as a distinct line item from your customers. Please note that travel and supply expenses should always be invoiced according to the main product's VAT rate, regardless of the original VAT rate of the expense.
Example 1: You bought a train ticket for €10 for work, including a 10% VAT. You are invoicing the customer for a cleaning service with a 24% VAT rate. If you want to invoice the train ticket from your customer, the train ticket portion is added to the invoice as follows: €10 + VAT 24% = €12.40
Example 2: You traveled to another location for work, incurring kilometer allowances of €100 and per diems of €51. You are invoicing the customer for a cleaning service with a 24% VAT rate. If you want to invoice the travel expenses from your customer, the travel expenses portion is added to the invoice as follows: €100 + €51 + VAT 24% = €187.24