Remove completed ToDo from Calendar?

Remove completed ToDo from Calendar?

I use Zoho Mail with calendar, and use the Tasks/ ToDo through that (not Projects, CRM etc) .  I schedule tasks so they are in my calendar or at least show up at the top of the day.  I want completed tasks to NOT show in the calendar, it is very untidy having the completed tasks there just with strikethrough; if its completed I dont need to see it.
How do I do this.