This is so because in a neutral atom same number os protons and electrons cancel each other. therefore, neutrons have no charges
Any body is said to be neutral when no of +ve charges are equal to the no of -ve charges.Since neutron is a fundamental particle it cant be made from any other fundamental its charge is zero A neutron is NOT a fundamental particle. A neutron is a baryon which means it is made from 3 quarks.  Now the quarks that makes protons and neutrons are up and down quarks and they carry a charge.  Now up quarks has a charge of +2/3  down quarks has a charge of -1/3  So an arrangement of 2 down quarks and an up quark yields no net charge and you have a neutron.  An arrangement of 2 ups and a down, yields a charge of +1 and you have a proton.