Plazo

Plazo
 

El plazo para entregar la documentación termina el martes
How can I say "plazo" in that sentence.

The deadline for handing in the documents is Tuesday.
Tuesday is the last day to hand in the documents .

Both sentences you provided use correct translations of plazo. I've listed a few more below.

You have until Tuesday to hand in your documents.
The window for handing in your documents ends (on) Tuesday/lasts until Tuesday.
Your last window of opportunity for handing in documents is Tuesday.