Thanks for ur feedback, Edward, yes it sounds strange, in the EU it's common to have intracommunitary VAT numbers of entities in their correspondence, not sure what the legal firm is expecting. Coming from China I didn t find many offices willing to take care of my paperwork and tax advice ( got a contact through a mainland law firm which had a partnership in Spain).
Not sure that firm, which has been restructured recently, has much experience in those declarations especially when it involves non european assets. Asked one of their lawyers ( more specialized in tax matters, but who was assigned to my case) to help me interpret immigration requirements a while back and he got it quite wrong already, it was simpler than he'd understood ?!? So, yes, misinterpretation is quite possible.
Talked to the girl taking care of this and she said they would fill it without the TIN ( NIF more exactly, in spanish), and see what happens.
I suspect language is not the issue here as my spanish is fairly fluent btw ( while my portuguese is not, one reason I chose Spain over Portugal, but Portugal might have been a better choice otherwise)
People are friendly in Spain but bureaucracy highly unefficient, plus wealth tax on worldwide assets in most provinces doesn t help the reporting requirements.