Section 19: Effect of assessment by commissioner and payment of duty in accordance therewith

Every instrument bearing a certificate of a commissioner that it is not chargeable with duty or that it is duly stamped, or being stamped with the amount of duty assessed and certified by him shall be admissible in evidence and available for all purposes, notwithstanding any objection relating to duty:
Provided that an instrument upon which the duty has been assessed by a commissioner shall not be stamped otherwise than in accordance with the assessment of the commissioner.