How to get an invoice (VAT invoice) for your purchase?

Purchases on learn.supermemo.com
When placing an order, you need to tick the box next to the “I want to receive an invoice for my company” option and fill in the required details. 

After the purchase, an invoice with a Polish tax identification number (NIP) will be available in KSeF. It will not be available for download in SuperMemo under “More” > “Order history”. 

An invoice without a Polish NIP will be available in the Order history.

Purchases on Google Play
You can find instructions on how to obtain a company invoice here: https://support.google.com/googlepay/answer/7644144?hl=en 
Purchases in the App Store
You can find instructions on how to obtain a company invoice here: https://www.apple.com/shop/help/payments