(NH4)2SO4 is an ionic compound that dissociates itself upon its addition to the solvent to form a solution. When it is in the solution it forms ions. The balanced dissociation for for (NH4)2SO4 is
(NH4)2SO4 ---> 2NH4^+ + SO4^-2
The dissociation of (NH4)2SO4 forms 2 moles of ammonium ions (NH4^+) and 1 mole of sulfate ion (SO4^2-). It is already balanced.