Nobody on these forums works for Apple. I am in the USA and have no idea as to European laws about this. I think it would be highly unusual that Apple (or anybody for that matter) would not issue a receipt (note that an invoice and a receipt are not necessarily identical) for a purchase. You may be requesting something very specific, or maybe you are not going to an official Apple retailer. You would need to contact Apple support for your country to see if there is some special policy.
Refer to this page for Apple Support features ➔ Contact - Official Apple Support
Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
This page has telephone numbers for contacting Apple for support and service ➔ Contact Apple for support and service - Apple Support