Butons, take a look at:- http://www.pymesyautonomos.com/actualidad/te-interesa-cambio-de-numero-de-nif-a-partir-de-julio
However, the July referred to is July 2008 !
This is an online translation :
If you have a Private Civil Society, you should know that EHA/451/2008 ORDER of 20 February, the composition of the tax identification number of legal persons and entities without legal personality, which will enter into force regulating the July 1, 2008, introduces a number of changes in the tax identification numbers of some entities, especially affecting Private Civil Societies, which happen to have a key to having a G J.
Therefore, the Tax Agency held this June during an information campaign, and shall perform such modifications of NIF job involving a change of key, but no number or control character.
I attached summary table so you can see how it will affect the new rule to the entities and their NIF, in the first column you can see the key to be applied and which will apply.
Keys
Beginning July 1 AEAT sent by mail the accreditation cards to NIF offices of entities whose NIF has been modified.
The consequences of the modification of NIF will be:
As of July 1, 2008, the new NIF must be entered in all self-assessments, statements and written communications submitted to the tax authorities, as well as all documents or tax significance nature dispatched, regardless of or those that have their origin in these transactions before.
The new NIF shall communicate to others such as public records, banks, suppliers, customers etc..
In the case of change of NIF, if the entity has "digital certificate" issued by any of the Certifying Authorities shall apply for one NEW from July 1.
Another consequence is that there will have to adapt all external communication with your customers: invoices, etc ... plus ...