Form and substance? I don’t think so.
In contracts, the phrase is used exclusively in references to documents to be delivered, as in an opinion of counsel in form and substance satisfactory to the Buyer. As with most “doublets,” the suspicion is that it mainly serves to add a rhetorical flourish, an easy gravitas. On closer examination, that turns out to be the case.
I recall once whittling the phrase down to in form satisfactory to …. That prompted a colleague to suggest that form relates solely to the appearance of a document. What, the font? The margins? Justification? That would suggest that form is dispensable.
And if form means something more than that, then it would tread on the toes of substance. In that case, too, form would be dispensable.
One could presumably go with in substance satisfactory to …, but why not dispense with in substance, too? Saying an opinion of counsel satisfactory to the Buyer would seem sufficiently all-encompassing.
Of course, if you want to avoid any pre-closing haggling, your safest bet would be to attach the document in question as an exhibit. The contract would say that the document delivered has to be in the form of that exhibit or, if you want to build in some flexibility, in a form substantially similar to that exhibit. (Saying in the form of rather than in the form attached as saves you a word.) If the document relates to some future transaction the terms of which are as yet unknown, it may not be feasible to attach the document as an exhibit.
I checked some of my usual authorities—Black’s Law Dictionary, Garner’s A Dictionary of Modern Legal Usage, even Words & Phrases—and didn’t find any discussion of form and substance. If you know of any such discussion, please let me know.