Taxable person has to hand over the issued invoice to its customer (and not only on his request)

The prescribed fine for the customer who does not take over the invoice is set at EUR 40. For legal entities and sole proprietors who do not issue an invoice, fines range from EUR 1,500 to EUR 75,000, and for their responsible persons from EUR 800 to EUR 5,000

Source: info.leitnerleitner.com