Grant, I am presuming this relates to termination reason R18 under clause 91.6.
I have done a quick review of all the book literature on what is meant by ‘substantial’ work wrt to termination and can find no guidance on it, apart from :
- Rowlinson saying that it is open to interpretation and what is ‘substantial’ to one Party might well not be to another; and
- the Guidance Notes saying it is that judgement needs to be exercised.
For me, it is obviously over 50%, but could well be less.
However, what raises a question in my mind is the second part of your sentence in that you are either terminating the contract or not - there is no partial termination. So if you have terminated / been terminated, the work not stopped is also covered by that termination. Likewise, if a ‘substantial’ part of the work is still on hold, then the termination procedures would still apply.
Do you have more detail as I may be answering a different scenario to the one you have in reality ?