What kind of information may be required to a taxpayer?
It is important to define the term «tax significance» in order to prevent the Administration from violating the right to privacy protected by Article 18.1 CE, since this can only be carried out with significant tax data and information. If the Administration had the power to require any information regardless of whether its content violates or not the fundamental rights, the taxpayer would be helpless before the power of the Administration.
The Audiencia Nacional (Spanish High Court) in its judgment passed on the 8th of May 1994, states that the tax-significant information is the information which involves those events or acts that may be useful to the Administration in relation to fundamental rights, and in accordance with the Law, to determine whether certain people comply with the obligation set forth in Article 31.1 of the Constitution regarding the contribution to sustain public expenditure according to their economic capacity and power.
It is important to note that when the Administration requests information, it shall specify as clearly and precisely as possible the reasons for this action, even if later on the information gathered cannot be used.
The Supreme Court states that the tax-significant information can be defined as the quality of events or acts that may be useful to the Administration to learn whether certain individuals comply with the obligations set forth under Article 31.1 CE of contribution with public expenditure according to their economic capacity and power, in accordance with the Law. The usefulness of this information can either be «direct» (when the requested information relates to taxable events, i.e. activities, entitlements, actions or events subject to tax laws) or «indirect» (when the requested information relates only to collateral data, which may indicate the Administration to search for allegedly undeclared taxable events).
Therefore, in order for the Administration to require information, this data must be tax-significant.