The state is targeting a new group of alleged tax deadbeats: elderly residents with 30-year-old bills — and little chance of finding the paperwork to rebut their cases.

They include an 85-year-old retired Army major from Queens who says he is worried sick after being told he has an outstanding bill from 1975 that, with interest, has ballooned to more than $29,000.

“If I owed them that much, why didn’t they tell me before?” said Luther Gatling of Rochdale Village.

Thousands of tax bills went out in recent weeks to individuals and former business owners with accounts still open with the state. Many of the invoices target elderly people who say they settled their accounts years ago.

Gatling’s notice said that, under a new state debt-forgiveness program, if he acts before March 15, he will have to pay only about $6,500.

A spokeswoman for the state Taxation Department said she could not comment on a private tax bill.