PC giant Valve has updated its guidelines for selling season passes on Steam. 

Per new guidance on Steamworks, developers and publishers have to commit to a release date when advertising upcoming content such as season passes on a game's store page. If companies are not able to "clearly communicate" when this upcoming content will be landing, Valve says they should not be selling or allowing pre-orders for it. 

Developers and publishers can leave a vague release window – such as quarter, year or season – as well as a precise date for the upcoming content. 

"By offering a Season Pass, you are promising future content," Valve wrote. 

"In the process of launching a Season Pass you will be asked to commit to a launch timing for each content release in the Season Pass. That launch timing is a commitment to both customers and Steam.

"If you aren't ready to clearly communicate about the content included in each DLC AND when each DLC will be ready for launch, you shouldn't offer a Season Pass on Steam."