This microsimulation model of the tax-benefit system in Guatemala is the companion to the following paper (which has to be cited when using the model): Alberto Castañón-Herrera and Wilson Romero (2012), “A microsimulation model for Guatemala: the case of direct and indirect taxes”, in Carlos M. Urzúa (ed.), Fiscal Inclusive Development: Microsimulation Models for Latin America, Mexico City: ITESM-IDRC-UNDP, pp. 87-100. The program is free software and it is written using Excel. It can be modified under the terms of the GNU General Public License. The program is distributed in the hope that it will be useful to modelers, but without any warranty whatsoever.