A small update on non-residents tax submissions.
'Self-assessment' returns now have to be initially filed direct on line on the AEAT site using the online Form 210, and once that is done they are then directly"saved" into the AEAT database. At same time, a unique receipt reference number is then issued to acknowledge "filing" of the return , with copies of the completed self-assessment form(s) also made available to one by the site (with the unique reference number on them) which can then be saved and/or printed and used to pay in the bank in normal way.
There are a number of other payment options too including transferring monies in from an institution abroad etc.. the old paper 210 forms and the NIE identification "stickers" are no longer available from Hacienda.
Interrogating the AEAT site in search of 210 form etc. seems to work best under Internet Explorer and may require downloading of a small executable file (configuradorAEAT.exe) which is associated with site security certificates I think.
Managed to pay our due non-residents tax this morning in bank, so the new 'system' does work.