The tax and benefit system probably affects men and women differently because of the differences in living situations and behaviours that mean that men and women do not enjoy the same tax arrangements, and do not necessarily respond in the same way to changes in public policy. However, identifying the effects of a change to our tax and benefit system on the inequalities between men and women is a relatively complicated process: because men and women live and interact in the same collective fiscal entities (family or other household units), resources are often pooled, even if only partially. In order to measure the effects on an individual level of a change to the tax and benefit system, we must first investigate how resources are allocated and the tax burden is shared among the individuals of the household receiving said benefits or liable for those tax payments. We propose a methodology based on four different rules of distribution, which gives us intervals for the effect of a budgetary measure on women on the one hand, and for men on the other. Applied to the income tax reform of 2015, we find that this policy would have resulted in higher average gains for men, of between 1.20 and 8.10 euros per year. • A gender analysis is obligatory today for any new bill, but putting it into practice in the case of bills in the area of public finance remains unsatisfactory. • Identifying the individual effect of socio-fiscal reform requires an understanding of how income, particularly taxes and benefits, is shared among members of a family or other fiscal unit. At present, there are few studies that show such distribution in detail. • A multi-method approach, using different hypotheses about income distribution within collectivities and comparing their results, gives us a value interval in which the real effect of a budgetary measure on subgroups can be found. • We observe that, regardless of the hypothesis used about the pooling of resources within the fiscal household, the gains associated with the 2015 income tax reform are slightly higher for men.