ISNetworld is a prequalification system that is aligned to the specific customer requirements. It's not like Impac or Sitewise where it just gives you a percentage out of 100 and you can share that with other contractors.

For example we engage with five different companies through ISNetworld and, while there are similarities for the different entities, there are customer specific requirements for each one as well. As such you couldn't really use an ISN certificate as a prequal for a customer that's not using ISN itself.

For the construction industry, the team at CHASNZ are building a cross-recognition scheme to take this type of confusion out of the system. You can find out more here: Tōtika - Industry pre-qualification cross recognition

does that mean you have to "reapply" for each separate principal using ISNetWorld as their pre-qualification provider? Or do you just have to answer the unique questions for each separate submission?

You just have to answer a base questionnaire and a few unique ones. The score you're given is unique though as the different companies apply different weightings on the different sections