The possessive adjective

Hi! How are you?

We can say: ‘Someone forgot his luggage’. Or
‘Someone forgot her luggage’
Even, we could say 'Someone forgot their luggage.

But can we say:

‘One has to show his/her pass at the door’

Or should it be ‘One has to show ONE?S pass
at the door’?

Thanks a lot!

Jes?s

Hi Jesus

For relatively informal language, I would use the word “you” instead of the word “one”:

You have to show your pass at the door.

For more formal language (signs, regulations, etc.), the passive is usually used:

Passes must be shown at the door.

Amy