I think you must be on a different thread to me.
Rolley started this thread by questioning why (and if in fact it was correct) that an individual's 720 should declare 100% of the funds in a joint account that is only 50% theirs.
Kathyslad responded to say this is correct
Baz joined in expressing similar puzzlement as to why joint assets should be reported this way, and what the tax implications could be.
Kathyslad explained that at this time the 720 declaration has no direct effect on one's tax situation.
I chipped in to try to help clarify it, but agreed that the information requested, and the way that it must be declared, is somewhat concerning to some of us.
Baz suggested that they wouldn't be asking for this info if they didn't have in mind some future use (implying a new form of taxation)
Kathyslad pointed out that it's useful already, for them to check that correct taxes are paid on income, capital gains and inheritance etc.
And then YOU offered some curious advice about leaving Spain just as you are about to breath your last (a time at which it's probably too late to make such a decision) in order to...what? Make sure that some other jurisdiction claims taxes upon your death rather than Spain? You suggest that the 720, by making all your worldwide assets known to Spain, means that you would have to pay death duty on those assets, clearly implying that without the presence of a similar form of reporting, either here or in another country, you would condone "hiding" those assets to avoid IHT. Strangely out-of-character advice from you. And I still can't make any connection to the comment about CGT on the sale of Spanish property, to the 720. It may not be factually incorrect, but as you yourself said, "Asset Declaration, at present, has nothing to do with what tax one pays". Surely that applies to CGT as much as any other tax, so where's the relevance? And anyway, the 720 is only about overseas assets, so has no relevance to CGT on Spanish property.
Sorry John, I just can't see what your comments have to do with the original question, or indeed the whole asset reporting topic at all. I'm obviously still missing something!