Representative assessee recovery rights: entitlement to recover or retain sums paid and secure an assessing officer certificate to warrant retention. A representative assessee who pays any sum under the Act may recover that sum from the person on whose behalf it was paid or retain an equivalent amount from moneys in his representative capacity. A representative, or one who expects to be assessed as such, may retain from monies payable to the principal an amount equal to his estimated liability; if there is disagreement, the Assessing Officer may issue a certificate stating the amount to be retained pending settlement, which limits recovery except where the representative holds additional assets of the principal.