Based on a literature review this paper proposes a novel division of the factors that shape tax morale, including them in three dimensions: individual, social and institutional. Then we determine empirically the influence of each of these dimensions on Spaniards tax morale. The exercise is perfor - med for the period 2003-2010 with the Fiscal Barometer database provided by the Spanish Institute for Fiscal Studies. Besides a probit estimation, common in the literature, an OLS regression is carried out to estimate the impact of a tax morale indicator constructed with the principal components technique. Overall, the results achieved substantially confirm the theoretical predictions. Tax morale in Spain is influenced by factors belonging to the three dimensions identified.

Key words: Tax Morale, Spain, probit models, multilevel models, principal components.
JEL Classification: H26.