We are currently writing functional and technical specifications in a two column format; summary sentence and technical detail. The details often refer to an appendix with diagrams, layout designs ect.

However I am struggling with what tense to write it in:

With past tense as if the work is done I struggle to show highlight extensions of exiting work. Future tense as in it needs to do X starts to sound like a to do list or Tense neutral very hard as it has either going to be done or is done.

To add further confusion this specification may be read by people who do not have English as a first language.