[Klarna][Checkout v2] Whether a «unit_price» includes «discount_rate» or not?

Not.

An example of Klarna’s calculations:

"discount_rate": 700,
"quantity": 2,
"tax_rate": 2500,
"total_price_excluding_tax": 9028,
"total_price_including_tax": 11285,
"total_tax_amount": 2257,
"unit_price": 6067

https://developers.klarna.com/en/se/kco-v2/checkout-api#cart-item-object-properties

See also: