Last year 2013 by Real Decreto 828/2013, the Spanish Government passed a new formal obligation for this kind of entrepreneurs that calculate their activities by the system called “modulos”
The novelty is not the fact that they have to fulfill throughout the year a book of the invoices they received from their suppliers for the services and goods that they use in their activity.
That obligation already existed and it was necessary to make the final calculations of the VAT to pay at the end of the year.
The novelty is that for the first time these entrepreneurs will have to fulfill form 347 during February 2015 for the acquisition of the services and goods that have to be register on the book of invoices received.
So, in order to now wait until the end of the year, we recommend you to fulfill that book carefully throughout the year, as figures declared will have to match with the figures the suppliers have as well.