Travel / Polish Trains (Intercity - Return Tickets Query) [4]

Dzień dobry!

I am visiting Poland next month and am looking in to booking a train ticket from Kraków to Warsaw. I'm just going to Warsaw for the day so was wondering if Polish train companies have return tickets or whether it is necessary to buy two single tickets?

I had a look on the: intercity.pl/en/ web page but could only seem to book two single tickets.

Ollie