"Na sprzedaż"

Translation: For sale

[Joridiy]

In Spanish war say «en venta», literally the same here :)

[AlisonEtter]

Isn't on sale the same as for sale?

[Jellei]

I think it depends on the dialect, but as far as I know it is in British English. Added now.

Just please note that the Polish phrase doesn't mention anything about lower prices, which is how many people would understand 'on sale'.