For the federal return, IRS Schedule R Instructions, page 2: What is permanent and total disability? These instructions include a physician's statement on page 4 that a doctor can use to certify the disability.
For Georgia, the person must be determined as disabled by the Social Security Administration per Georgia Regulation 560-7-8-.43
To determine if your wife would qualify for disability according to Social Security, see this SSA.GOV resource: How you qualify
IRS: Disability Related Products
IRS: More information for people with Disabilities
2019 Georgia IT-511 Individual Income Tax Booklet
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