Disability deduction entitles certified resident individuals to specified tax relief subject to prescribed medical certification and renewal requirements. A resident individual certified by a medical authority as a person with disability or person with severe disability is entitled to a specified deduction while computing total income, subject to furnishing the medical certificate in the prescribed form and manner with the return of income; if the certificate requires reassessment after a specified period, the deduction is disallowed for years after expiry unless a renewed certificate is furnished. Definitions for disability, medical authority and the covered persons are those set out in the statute's definitional provision.