Here is an image I snagged from the internet, male left, female right. All males will have a curly tail eventually, but it takes awhile to grow in. My drake lost his curl during molt, so you could have a drake even if you don't see a curl

As the males mature, their feathers will look more like the one in the photo below. I believe though, like other breeds, the males will undergo an eclipse molt in fall typically. Your best bet is voice sexing when they are young and don't have their full adult plumage.
@snow5164 at 4 months I'm pretty sure a khaki drake would look different from a hen as well as sound different.
@chickens really do you know at what age the feathers/colors would be different for a drake vs. hen? My khakis are both hens so I'm not sure at what age it would have been obvious if they were not!
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