When determining the surface charge and pKa values of colloidal particles, the most popular existing methods are conductometric and potentiometric titration. However, the dissociation of the closely packed charged species on a colloidal particle is suppressed due to a phenomenon called counterion condensation which directly influences the titration curves. The phenomenon has been mathematically described for dissolved polyelectrolytes but it has never been applied to describe the genuine charge of nanoparticles or the seemingly anomalous tendencies in the conductivity of their aqueous suspensions. Here, we have applied the counterion condensation theory, together with classical Poisson-Boltzmann statistics of the electric double layer, to explain the dissociation behavior of phosphorylated, divalent CNCs. The results address the genuine charge of CNCs which is a decisive factor in many of its properties, including colloidal stability, ion exchange capacity, or the propensity to self-assemble.