I want to know, what is the correct form grammatically.
Had I not had cash on me, I would have been in deep trouble
or
Had I not have cash on me, I would have been in deep trouble.
Is this a less used form & perhaps, something like the following?
Did I not have cash on me, I would have been in deep trouble
Best Answer
This is a form of the subjunctive, and is quite uncommon.
This form of the subjunctive is formed by inverting the subject and auxiliary verb "had" in the past perfect. So the first word must be "had" and the main verb must be in the past participle form. It is easier to follow if the main verb isn't a form of "have"
Using the basic form of the verb is not grammatically correct
Using "have" forms a question, not a subjunctive:
The "had" subjunctive is a rare feature of English. You can nearly always replace it with an "if":
So in your example, the only possible form is:
The others are either ungrammatical *(had I not have cash), or are a question (did I not have cash?)
But you could say: