Our company supplies pencil pleat curtains. If our installation instructions give consumers the option to cut off or tie off the excess cord, do we need to provide a cleat and screws?

If your instructions specify that excess cord must be cut off (i.e. you do not give any other option) then you are not required to provide cleats and screws.

However, if your instructions provide the option to cut off or tie off the cord then you must provide cleats and screws.