Resumen
This paper analyses the Spanish tax administration, evaluating the relative efficiency of each of the regional offices that are its constituent parts via output-oriented two-stage data envelopment analysis. In the study, a total of 47 regional offices were analysed, considering three inputs: 1) current expenditure in goods and services; 2) number of tax returns processed in terms of the two main direct taxes; and, 3) personnel numbers. Revenue resulting from tax assessments was considered as output. The analysis shows that the efficient action of regional offices might have increased by 21.6% the results of the management of this administration.